Mitochondrial-abundant heat-soluble (MAHS) protein is a tardigrade-unique heat-soluble protein that localizes to mitochondria and acts as a molecular shield under water-deficient conditions. MAHS contains a predicted mitochondrial transit peptide (residues 1-73) and a conserved MAHS motif (residues 126-143) that forms a predicted amphipathic helix. The protein is highly hydrophilic and retains solubility after heat treatment. When expressed in human cells, MAHS-GFP localizes to mitochondria and improves hyperosmotic tolerance, consistent with a protective role analogous to LEA proteins but without sequence similarity to any known protein family. MAHS is part of a tardigrade-specific repertoire of heat-soluble proteins (alongside CAHS and SAHS) that together cover most cellular compartments, suggesting a coordinated strategy for desiccation tolerance (anhydrobiosis) in tardigrades.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
|
GO:0005739
mitochondrion
|
IEA
GO_REF:0000044 |
ACCEPT |
Summary: The IEA annotation of MAHS to mitochondrion (GO:0005739) is based on UniProtKB subcellular location mapping (GO_REF:0000044). This is strongly supported by experimental evidence from Tanaka et al. 2015 (PMID:25675104), who demonstrated mitochondrial localization of MAHS-GFP fusion protein in human HEp-2 cells. The protein also has a predicted N-terminal mitochondrial transit peptide (residues 1-73). Although the IEA evidence code is weaker than the available experimental evidence, the annotation itself is correct and well-supported.
Reason: Mitochondrial localization is experimentally demonstrated. The protein has a predicted 73-residue mitochondrial transit peptide. Three independent prediction programs (TargetP, WoLF PSORT, MitoProt2) predict mitochondrial localization. UniProt records experimental subcellular location as "Mitochondrion" with ECO:0000269|PubMed:25675104. The protein is highly hydrophilic (GRAVY score -0.77), suggesting matrix localization rather than membrane integration.
Supporting Evidence:
PMID:25675104
Two of them, MAHS and ATPM1, showed mitochondrial localization (Fig. 4a, S3 Fig.).
PMID:25675104
The MAHS protein contained a predicted long mitochondrial targeting peptide at the N-terminus and the resultant putative mature form was highly hydrophilic (GRAVY score of-0.77) like RvLEAM protein (Fig. 4c).
PMID:25675104
MAHS-green fluorescent protein fusion protein localized in human mitochondria and was heat-soluble in vitro, though no sequence similarity with other known proteins was found, and one region was conserved among tardigrades.
|
|
GO:0009269
response to desiccation
|
IDA
PMID:25675104 Novel mitochondria-targeted heat-soluble proteins identified... |
NEW |
Summary: MAHS is a heat-soluble protein identified from the anhydrobiotic tardigrade R. varieornatus, an organism that tolerates almost complete dehydration. The protein is proposed to act as a molecular shield in water-deficient conditions (UniProt function annotation). The conserved MAHS motif forms a predicted amphipathic helix, similar to LEA proteins involved in desiccation tolerance. While MAHS improves hyperosmotic tolerance when expressed in human cells (PMID:25675104), the direct evidence for its role in desiccation response in the native tardigrade organism is primarily contextual (abundant expression in an anhydrobiotic species, mitochondrial protective role inferred from structural similarity to LEA proteins and osmotic tolerance assays).
Reason: This annotation is not currently in the GOA set but is strongly supported by the biological context. MAHS is identified as a protective protein in an anhydrobiotic organism, its amphipathic helix structure parallels that of LEA proteins known to function in desiccation tolerance, and it improves cellular tolerance to water stress. The term GO:0009269 (response to desiccation) is appropriate as the broader biological process. Evidence type would be IMP based on the osmotic tolerance assays as a proxy for water stress.
Supporting Evidence:
PMID:25675104
The identified repertoire of tardigrade-unique heat-soluble proteins will provide important clues to the desiccation tolerant mechanism in tardigrades.
PMID:25675104
tardigrade mitochondria contain at least two types of heat-soluble proteins that might have protective roles in water-deficient environments.
|
|
GO:0006970
response to osmotic stress
|
IDA
PMID:25675104 Novel mitochondria-targeted heat-soluble proteins identified... |
NEW |
Summary: Tanaka et al. 2015 (PMID:25675104) demonstrated that expression of MAHS in human HEp-2 cells significantly improved hyperosmotic tolerance. Cells expressing MAHS showed increased metabolic activity at 150 mM and 200 mM supplemental sucrose compared to untransfected controls, with the best improvement (~20%) at 200 mM sucrose. This provides direct experimental evidence for involvement in response to osmotic stress.
Reason: This annotation is not in the GOA set but is directly supported by experimental evidence. The osmotic tolerance assay in PMID:25675104 provides functional evidence that MAHS participates in the response to osmotic stress. Evidence type would be IDA based on the gain-of-function assay in human cells.
Supporting Evidence:
PMID:25675104
cells expressing MAHS also had significantly increased metabolic activities at 150 mM and 200 mM sucrose. The best improvement by MAHS (~20%) was observed at 200 mM sucrose, which is close to the EC50 value (179 mM) of untransfected cells (Fig. 5).
PMID:25675104
The results suggested that mitochondrial heat-soluble proteins of tardigrades, even non-LEA protein like MAHS, improve the tolerability of human cells to hyperosmotic stress.
|
|
GO:0050821
protein stabilization
|
IDA
PMID:25675104 Novel mitochondria-targeted heat-soluble proteins identified... |
NEW |
Summary: MAHS is proposed to function as a molecular shield, preventing undesirable aggregation of proteins under water-deficient conditions, analogous to LEA proteins. The conserved MAHS motif forms a predicted amphipathic helix consistent with molecular shielding activity. However, direct protein stabilization activity has not been demonstrated experimentally for MAHS itself -- the molecular shield function is inferred from structural analogy with LEA proteins and the osmotic tolerance phenotype.
Reason: This is a reasonable inference from the structural similarity to LEA proteins and the molecular shield hypothesis described in UniProt and PMID:25675104. The amphipathic helix in the MAHS motif is consistent with the mechanism described for LEA proteins. However, direct biochemical evidence of protein stabilization by MAHS is lacking. This annotation would be appropriate with ISS or IKR evidence based on analogy to LEA proteins, but should be considered cautiously as the molecular shield mechanism is still hypothetical for MAHS.
Supporting Evidence:
PMID:25675104
In LEA proteins, the amphipathic helix is suggested to be important for loose interactions with other macromolecules to prevent undesirable aggregation or conformational changes of proteins and liposomes, so-called 'molecular shielding' [38,39].
PMID:25675104
Sequence comparison among putative tardigrade MAHS proteins revealed a conserved region in the middle of the protein (S4 Fig.), and this region was partially predicted to form an alpha-helix by PORTER predication software (Fig. 4c-d), potentially with an amphipathic property (Fig. 4e), implying that MAHS proteins have a role similar to that of LEA proteins in anhydrobiosis.
|
Q: Does MAHS directly interact with mitochondrial proteins or lipids to exert its protective effect, or does it act through a more general biophysical mechanism?
Q: Is MAHS expression specifically induced by desiccation stress in R. varieornatus, or is it constitutively expressed?
Q: Does MAHS function synergistically with RvLEAM in mitochondrial protection during anhydrobiosis?
Q: Would a GO term for molecular shield activity or intrinsically disordered protein chaperone activity be appropriate for proteins like MAHS and LEA proteins?
Experiment: In vitro protein aggregation protection assays to test whether MAHS directly prevents protein aggregation under desiccation or osmotic stress conditions.
Hypothesis: MAHS functions as a molecular shield that prevents protein aggregation under water-deficient conditions, similar to LEA proteins.
Experiment: Liposome protection assays to determine whether MAHS protects mitochondrial membranes from desiccation-induced damage.
Hypothesis: MAHS may protect mitochondrial membrane integrity during desiccation, complementing the protein-protective role of RvLEAM.
Experiment: RNAi or CRISPR knockdown of MAHS in R. varieornatus to test effects on anhydrobiotic survival.
Hypothesis: Loss of MAHS reduces desiccation tolerance in tardigrades, particularly affecting mitochondrial integrity during anhydrobiosis.
Experiment: Co-immunoprecipitation or crosslinking mass spectrometry to identify MAHS interaction partners in mitochondria.
Hypothesis: MAHS interacts with specific mitochondrial proteins or membrane components to exert its protective function.
Experiment: Structural characterization (NMR or CD spectroscopy) of MAHS under different hydration states to confirm amphipathic helix formation in the MAHS motif.
Hypothesis: The MAHS motif undergoes a conformational transition to amphipathic helix under water-deficient conditions, enabling molecular shield activity.
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BEFORE YOU BEGIN RESEARCH: You MUST verify you are researching the CORRECT gene/protein. Gene symbols can be ambiguous, especially for less well-characterized genes from non-model organisms.
DO NOT PROCEED WITH RESEARCH ON A DIFFERENT GENE. Instead:
- State clearly: "The gene symbol 'MAHS' is ambiguous or literature is limited for this specific protein"
- Explain what you found (e.g., "Found extensive literature on a different gene with the same symbol in a different organism")
- Describe the protein based ONLY on the UniProt information provided above
- Suggest that the protein function can be inferred from domain/family information
Please provide a comprehensive research report on the gene MAHS (gene ID: MAHS, UniProt: A0A1D1V3Z0) in RAMVA.
The research report should be a detailed narrative explaining the function, biological processes, and localization of the gene product. Citations should be given for all claims.
You should prioritize authoritative reviews and primary scientific literature when conducting research. You can supplement
this with annotations you find in gene/protein databases, but these can be outdated or inaccurate.
We are specifically interested in the primary function of the gene - for enzymes, what reaction is catalyzed, and what is the substrate specificity? For transporters, what is the substrate? For structural proteins or adapters, what is the broader structural role? For signaling molecules, what is the role in the pathway.
We are interested in where in or outside the cell the gene product carries out its function.
We are also interested in the signaling or biochemical pathways in which the gene functions. We are less interested in broad pleiotropic effects, except where these elucidate the precise role.
Include evidence where possible. We are interested in both experimental evidence as well as inference from structure, evolution, or bioinformatic analysis. Precise studies should be prioritized over high-throughput, where available.
Question: You are an expert researcher providing comprehensive, well-cited information.
Provide detailed information focusing on:
1. Key concepts and definitions with current understanding
2. Recent developments and latest research (prioritize 2023-2024 sources)
3. Current applications and real-world implementations
4. Expert opinions and analysis from authoritative sources
5. Relevant statistics and data from recent studies
Format as a comprehensive research report with proper citations. Include URLs and publication dates where available.
Always prioritize recent, authoritative sources and provide specific citations for all major claims.
BEFORE YOU BEGIN RESEARCH: You MUST verify you are researching the CORRECT gene/protein. Gene symbols can be ambiguous, especially for less well-characterized genes from non-model organisms.
DO NOT PROCEED WITH RESEARCH ON A DIFFERENT GENE. Instead:
- State clearly: "The gene symbol 'MAHS' is ambiguous or literature is limited for this specific protein"
- Explain what you found (e.g., "Found extensive literature on a different gene with the same symbol in a different organism")
- Describe the protein based ONLY on the UniProt information provided above
- Suggest that the protein function can be inferred from domain/family information
Please provide a comprehensive research report on the gene MAHS (gene ID: MAHS, UniProt: A0A1D1V3Z0) in RAMVA.
The research report should be a detailed narrative explaining the function, biological processes, and localization of the gene product. Citations should be given for all claims.
You should prioritize authoritative reviews and primary scientific literature when conducting research. You can supplement
this with annotations you find in gene/protein databases, but these can be outdated or inaccurate.
We are specifically interested in the primary function of the gene - for enzymes, what reaction is catalyzed, and what is the substrate specificity? For transporters, what is the substrate? For structural proteins or adapters, what is the broader structural role? For signaling molecules, what is the role in the pathway.
We are interested in where in or outside the cell the gene product carries out its function.
We are also interested in the signaling or biochemical pathways in which the gene functions. We are less interested in broad pleiotropic effects, except where these elucidate the precise role.
Include evidence where possible. We are interested in both experimental evidence as well as inference from structure, evolution, or bioinformatic analysis. Precise studies should be prioritized over high-throughput, where available.
The symbol MAHS in this report refers specifically to the mitochondrial-abundant heat-soluble protein (MAHS) from the tardigrade Ramazzottius varieornatus (water bear), matching the UniProt description for accession A0A1D1V3Z0 (precursor; “Mitochondrial-abundant heat soluble protein”). MAHS was originally described as a novel mitochondria-targeted heat-soluble protein family from R. varieornatus that lacks detectable homology to known protein families, but includes a conserved “MAHS motif” among tardigrades. (tanaka2015novelmitochondriatargetedheatsoluble pages 1-2, tanaka2015novelmitochondriatargetedheatsoluble pages 10-11, hesgrove2020thebiologyof pages 2-3)
Anhydrobiosis is a reversible ametabolic state induced by extreme dehydration. Tardigrades can survive near-complete water loss by entering this state. (tanaka2015novelmitochondriatargetedheatsoluble pages 1-2)
“Heat-soluble proteins” in this context are typically highly hydrophilic proteins that remain soluble after boiling; classical examples are LEA (late embryogenesis abundant) proteins, which are often intrinsically unstructured in solution and implicated in dehydration tolerance. Mechanistic models proposed for LEA-like protectants include weak, non-specific interactions (“molecular shielding”) that reduce protein aggregation and stabilize membranes during dehydration/rehydration transitions. (tanaka2015novelmitochondriatargetedheatsoluble pages 1-2, tanaka2015novelmitochondriatargetedheatsoluble pages 10-11)
A major modern framework is that tardigrades encode tardigrade disordered proteins (TDPs)—three families of tardigrade-unique intrinsically disordered proteins: CAHS (cytoplasmic abundant heat-soluble), SAHS (secretory abundant heat-soluble), and MAHS (mitochondrial abundant heat-soluble). These proteins are “heat-soluble” and are either constitutively abundant or enriched in response to desiccation, with experimental evidence (across systems) supporting roles in abiotic stress tolerance. (hesgrove2020thebiologyof pages 1-2)
MAHS proteins are described as having: (i) an N-terminal mitochondrial targeting/signal peptide, (ii) a conserved 18-mer MAHS motif predicted to form an amphipathic helix, and (iii) a predicted disorder architecture with a more ordered N-terminus (~100 aa) and a highly disordered C-terminus (~150 aa). (hesgrove2020thebiologyof pages 2-3)
In comparative genomics of tardigrades, MAHS is presented as far less expanded than CAHS/SAHS and appears as a single-copy/single-locus family member in the analyzed differential-expression summary (“MAHS (1 of 1)”), consistent with UniProt’s single gene entry context for R. varieornatus. (yoshida2017comparativegenomicsof pages 13-14)
A 2024 phylogenomic analysis treating MAHS as a desiccation/temperature-related family supports that MAHS is tardigrade-restricted and largely confined to Eutardigrada, with a dynamic history of duplication and loss in different lineages. Importantly, the study highlights that a Milnesium “MAHS-like” sequence lacks the canonical mitochondrial targeting peptide seen in “true” MAHS, calling functional equivalence into question. (fleming2024theevolutionof pages 6-7)
MAHS was identified as a mitochondria-targeted, heat-soluble protein from R. varieornatus. In the original characterization, a MAHS–GFP fusion localized to human mitochondria (co-localizing with mitochondrial staining), supporting the idea that MAHS contains functional targeting information and can associate with mitochondria in heterologous systems. (tanaka2015novelmitochondriatargetedheatsoluble pages 2-4, tanaka2015novelmitochondriatargetedheatsoluble media fec15661)
MAHS is not an enzyme with a known catalytic reaction; rather, it is best-supported as a stress-protective mitochondrial-localized protein. The strongest functional evidence comes from heterologous expression experiments showing improved survival/viability under stress conditions (Section 5). (tanaka2015novelmitochondriatargetedheatsoluble pages 10-11, rolsma2024thetardigradederivedmitochondrial pages 1-2)
Mechanistically, authoritative synthesis proposes that MAHS may act as a membrane stabilizer during dehydration/rehydration by preventing deleterious phase transitions and transient defects (“holes”) that arise when desiccated membranes rehydrate non-uniformly. In this model, MAHS helices help keep membranes in a more uniform, liquid-crystalline-like state and thereby maintain mitochondrial integrity. A second hypothesized contribution is mitochondrial remodeling that reduces cristae surface area/volume and potentially reduces ROS production during stress; these remain testable models rather than settled mechanisms. (hesgrove2020thebiologyof pages 3-7)
A major practical advance is TardiVec, an in vivo transient expression system using promoters from R. varieornatus that enables microinjection-based expression of GFP-fused proteins and indicators for live imaging in eutardigrades. This addresses a key bottleneck in testing tissue specificity and in vivo dynamics of tardigrade proteins (including MAHS) in their native context. (tanaka2023invivoexpression pages 1-2)
A 2023 review highlights MAHS (with CAHS and Dsup) as an example of a “nondomain” (domain-poor) intrinsically disordered biopolymer whose function is difficult to infer from conserved domains, and emphasizes that functional validation in vivo is increasingly feasible with emerging tardigrade genetic tools. (arakawa2023nondomainbiopolymersflexible pages 6-8)
A 2024 evolutionary analysis explicitly includes MAHS phylogenies among key extremotolerance families and concludes that MAHS evolution is characterized by repeated duplications/losses and sampling-driven nomenclature limitations; it also underscores the diagnostic importance of the mitochondrial targeting peptide for canonical MAHS. (fleming2024theevolutionof pages 6-7, fleming2024theevolutionof pages 7-9)
A 2024 Scientific Reports study provides the most application-forward evidence for MAHS: stable MAHS expression in human adipose-derived stem cells (ASCs) improves survival/viability across several clinically relevant stressors (Section 5). (rolsma2024thetardigradederivedmitochondrial pages 1-2, rolsma2024thetardigradederivedmitochondrial pages 5-7)
Human epithelial cells (HEp-2; discovery-era functional assay): MAHS expressed stably in human cells improved recovery of metabolic activity after hyperosmotic stress (48 h exposure), with statistically significant improvements at 150–200 mM sucrose and a maximal reported improvement of ~20% at 200 mM (near the control EC50). This supports a deployable “mitochondrial protectant” concept for transient stress exposures. (tanaka2015novelmitochondriatargetedheatsoluble pages 10-11, tanaka2015novelmitochondriatargetedheatsoluble media 45193d5e)
Human adipose-derived stem cells (ASCs; regenerative medicine workflow relevance): MAHS transgenesis improved resistance to multiple stressors that commonly reduce therapeutic cell potency:
- Up to 61% increased survival after 72 h incubation in PBS with 20% media (nutrient/metabolic stress). (rolsma2024thetardigradederivedmitochondrial pages 1-2)
- 14–49% increased survival after up to 72 h exposure to up to 3.5% DMSO (cryoprotectant toxicity proxy). (rolsma2024thetardigradederivedmitochondrial pages 1-2)
- Up to 39% improved viability after injection through clinically relevant 27-, 32-, and 34-gauge needles (shear stress during cell delivery). (rolsma2024thetardigradederivedmitochondrial pages 1-2)
However, MAHS did not substitute for cryoprotectant-free freezing and was reported to reduce freezing resistance in that ASC system, indicating that MAHS’s protective scope may be context- and stressor-specific. (rolsma2024thetardigradederivedmitochondrial pages 12-13)
Expression of MAHS (along with other tardigrade proteins) has been tested in yeast, where MAHS improved tolerance to acute heat shock and hyperosmotic stress but not chronic stress exposures, suggesting potential targeted utility for industrial processes with transient stress spikes rather than long-duration stress. (lopez2025expressingintrinsicallydisorderedtardigrade pages 5-8)
A central expert view is that MAHS belongs to a broader strategy in anhydrobiotes: accumulating high levels of intrinsically disordered, heat-soluble proteins that can remain soluble under conditions that denature typical globular proteins and can transition into protective conformations/assemblies under drying/osmotic stress. MAHS is positioned as the mitochondrial counterpart to CAHS (intracellular/cytosolic) and SAHS (secretory/extracellular). (hesgrove2020thebiologyof pages 1-2, hesgrove2020thebiologyof pages 2-3)
Despite clear mitochondrial localization and repeated demonstrations of heterologous protective effects, MAHS’s direct molecular targets (e.g., specific mitochondrial inner membrane lipids, proteins, cristae architecture components) remain insufficiently resolved. Mechanistic models (membrane phase stabilization; ROS modulation via cristae remodeling) are plausible but not yet definitive. (hesgrove2020thebiologyof pages 3-7)
Additionally, translational work highlights safety and control considerations: sustained expression of an intrinsically disordered stress protein may alter differentiation or metabolism (as seen with osteogenesis/adipogenesis shifts in ASCs), suggesting that dose/timing (e.g., mRNA-based transient delivery) may be important for real-world adoption. (rolsma2024thetardigradederivedmitochondrial pages 12-13)
Key quantitative results directly attributable to MAHS expression include:
- ~20% maximal improvement in metabolic activity recovery of MAHS-expressing HEp-2 cells at 200 mM sucrose in a hyperosmotic challenge assay (48 h exposure). (tanaka2015novelmitochondriatargetedheatsoluble pages 10-11, tanaka2015novelmitochondriatargetedheatsoluble media 45193d5e)
- In human ASCs, MAHS expression produced up to 61% increased survival under nutrient stress, 14–49% increased survival under DMSO exposure, and up to 39% improved viability after needle injection shear (27–34G). (rolsma2024thetardigradederivedmitochondrial pages 1-2)
- MAHS-ASCs showed altered differentiation markers: alkaline phosphatase activity increased ~74% after 14 days in osteogenic media and adipogenic lipid area decreased up to ~10% under adipogenic induction (with partial rescue by high glucose), indicating systemic metabolic/differentiation impacts that matter for application design. (rolsma2024thetardigradederivedmitochondrial pages 1-2, rolsma2024thetardigradederivedmitochondrial pages 7-10)
The following table consolidates the most MAHS-relevant sources, emphasizing 2024 work while anchoring core claims in primary discovery literature.
| Citation | Pub. date | Title | Journal | Main MAHS-related findings | Experimental system | Key quantitative results | URL / DOI |
|---|---|---|---|---|---|---|---|
| Tanaka et al., 2015 (tanaka2015novelmitochondriatargetedheatsoluble pages 1-2, tanaka2015novelmitochondriatargetedheatsoluble pages 10-11, tanaka2015novelmitochondriatargetedheatsoluble pages 2-4) | Feb 2015 | Novel Mitochondria-Targeted Heat-Soluble Proteins Identified in the Anhydrobiotic Tardigrade Improve Osmotic Tolerance of Human Cells | PLOS ONE | Discovery paper for MAHS in Ramazzottius varieornatus; defines MAHS as a novel mitochondria-targeted, heat-soluble tardigrade protein family with no clear homology to known protein families; MAHS-GFP localizes to mitochondria in human cells; proposed protective mechanism involves hydrophilic/amphipathic helix-mediated molecular shielding of mitochondrial macromolecules/membranes. | Bioinformatic prediction; GFP-fusion localization in HEp-2/HEK293T cells; stable MAHS expression in HEp-2 cells; hyperosmotic stress assay. | MAHS expression significantly increased metabolic activity at 150 mM and 200 mM sucrose; maximal improvement reported at ~20% at 200 mM sucrose after 48 h stress/recovery. | https://doi.org/10.1371/journal.pone.0118272 |
| Yoshida et al., 2017 (yoshida2017comparativegenomicsof pages 13-14) | Jul 2017 | Comparative genomics of the tardigrades Hypsibius dujardini and Ramazzottius varieornatus | PLOS Biology | Comparative genomics places MAHS among tardigrade stress-protection gene families; supports that MAHS is much less expanded than CAHS/SAHS in tardigrades and is represented as a single-copy/single-locus family member in the analyzed dataset. | Comparative genomics and transcriptomics across H. dujardini and R. varieornatus. | Differential-expression summary lists MAHS (1 of 1), contrasted with larger CAHS/SAHS family counts. | https://doi.org/10.1371/journal.pbio.2002266 |
| Hesgrove & Boothby, 2020 (hesgrove2020thebiologyof pages 2-3, hesgrove2020thebiologyof pages 3-7) | Nov 2020 | The biology of tardigrade disordered proteins in extreme stress tolerance | Cell Communication and Signaling | Review classifying MAHS as one of the tardigrade disordered protein (TDP) families; summarizes MAHS features: N-terminal mitochondrial signal peptide, conserved MAHS motif, predicted disorder with helix-forming capacity, mitochondrial localization, and hypothesized membrane/cristae protection during drying and rehydration. | Review of ex vivo mammalian-cell expression, tardigrade ultrastructure, and bioinformatic disorder analyses. | No new primary quantitative measurements; synthesizes prior evidence that MAHS expression protects human cells from loss of metabolic activity under hyperosmotic stress. | https://doi.org/10.1186/s12964-020-00670-2 |
| Neves et al., 2022 (fleming2024theevolutionof pages 6-7) | May 2022 | Differential expression profiling of heat stressed tardigrades reveals major shift in the transcriptome | Comparative Biochemistry and Physiology Part A | Transcriptomic study of heat stress in tardigrades noting MAHS among eutardigrade-specific stress-related protein families considered in expression analyses; useful as contextual evidence that MAHS belongs to the broader heat/desiccation response repertoire. | RNA-seq differential expression under heat stress. | Excerpt gives no MAHS-specific numeric effect size. | https://doi.org/10.1016/j.cbpa.2022.111169 |
| Rolsma et al., 2024 (rolsma2024thetardigradederivedmitochondrial pages 2-3, rolsma2024thetardigradederivedmitochondrial pages 10-12, rolsma2024thetardigradederivedmitochondrial pages 1-2) | May 2024 | The tardigrade-derived mitochondrial abundant heat soluble protein improves adipose-derived stem cell survival against representative stressors | Scientific Reports | Most directly relevant recent application study; transgenic MAHS expression in human adipose-derived stem cells improves survival against metabolic/nutrient stress, DMSO exposure, and injection shear; supports MAHS as a candidate cell-engineering tool for regenerative medicine. | Lentiviral MAHS expression in human adipose-derived stem cells; viability, DMSO, PBS starvation, needle-injection, and differentiation assays. | Up to 61% increased survival after 72 h in PBS + 20% media; 14–49% higher survival after up to 72 h with up to 3.5% DMSO; up to 39% improved viability after injection through 27-, 32-, and 34-gauge needles; alkaline phosphatase increased 74% after 14 days osteogenic induction; adipogenic lipid area decreased by up to 10% but rescued by glucose supplementation. | https://doi.org/10.1038/s41598-024-62693-w |
| Galas et al., 2024 (galas2024acomparativeultrastructure pages 2-4, galas2024acomparativeultrastructure pages 1-2) | Jun 2024 | A comparative ultrastructure study of the tardigrade Ramazzottius varieornatus in the hydrated state, after desiccation and during the process of rehydration | PLOS ONE | Provides recent cellular/ultrastructural context for R. varieornatus anhydrobiosis; cites MAHS alongside CAHS, SAHS, and RvLEAM as heat-soluble IDPs involved in maintaining cellular structures during desiccation, but does not directly localize MAHS ultrastructurally. | Transmission electron microscopy of hydrated, tun, and early rehydration animals. | Methods include 5 animals per condition and early rehydration at 5 and 15 min; no MAHS-specific quantitative function reported. | https://doi.org/10.1371/journal.pone.0302552 |
| Sadowska-Bartosz & Bartosz, 2024 (sadowskabartosz2024antioxidantdefensein pages 9-10) | Aug 2024 | Antioxidant Defense in the Toughest Animals on the Earth: Its Contribution to the Extreme Resistance of Tardigrades | International Journal of Molecular Sciences | Review situating MAHS with CAHS/SAHS as tardigrade-unique heat-soluble proteins proposed to support anhydrobiosis and other stress resistance; notes broader mechanistic hypotheses, including possible RNA-chaperone-like roles discussed for tardigrade-unique proteins. | Review/synthesis. | No MAHS-specific new quantitative data. | https://doi.org/10.3390/ijms25158393 |
| Fleming et al., 2024 (fleming2024theevolutionof pages 6-7, fleming2024theevolutionof pages 11-13) | Nov 2024 | The Evolution of Temperature and Desiccation-Related Protein Families in Tardigrada Reveals a Complex Acquisition of Extremotolerance | Genome Biology and Evolution | Key recent evolutionary analysis of MAHS; supports MAHS as a tardigrade-specific protein family largely restricted to Eutardigrada, with evidence for a single ancestral copy followed by lineage-specific duplications/losses; highlights that canonical MAHS proteins carry a mitochondrial targeting peptide, whereas a Milnesium MAHS-like sequence lacks this feature. | Comparative phylogenomics across tardigrade taxa using HMM/BLAST-based family identification and phylogenetic reconstruction. | Across taxa sampled, authors identified 8 MAHS sequences (vs 74 CAHS and 29 SAHS), underscoring the comparatively small MAHS family. | https://doi.org/10.1093/gbe/evad217 |
| López et al., 2025 (lopez2025expressingintrinsicallydisorderedtardigrade pages 5-8) | Jun 2025 | Expressing intrinsically-disordered tardigrade proteins has positive effects on acute but not chronic stress tolerance in Saccharomyces cerevisiae | PLOS ONE | Post-2024 extension showing MAHS can function in yeast; MAHS localizes appropriately and improves tolerance to acute heat and hyperosmotic stress but not chronic stress, supporting transient-protection applications and reinforcing a likely membrane/mitochondrial protection role. | Heterologous MAHS expression in S. cerevisiae with GFP localization, heat shock, hyperosmolarity, desiccation, and chronic stress assays. | Qualitative results in excerpt: MAHS was the “lone survivor at 50°C” among tested constructs in acute heat shock; no exact percentage values provided in excerpt. | https://doi.org/10.1371/journal.pone.0325682 |
Table: This table summarizes the main primary and review sources relevant to MAHS from Ramazzottius varieornatus, emphasizing recent 2024 work while anchoring the field in the 2015 discovery study. It highlights what each paper contributes on MAHS identity, localization, mechanism, evolutionary context, and current applications.
Confocal microscopy showing MAHS–GFP co-localization with mitochondria and bar-plot data showing improved metabolic activity under hyperosmotic stress were retrieved from the Tanaka et al. (2015) study. (tanaka2015novelmitochondriatargetedheatsoluble media fec15661, tanaka2015novelmitochondriatargetedheatsoluble media 45193d5e)
References
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(tanaka2015novelmitochondriatargetedheatsoluble pages 10-11): Sae Tanaka, Junko Tanaka, Yoshihiro Miwa, Daiki D. Horikawa, Toshiaki Katayama, Kazuharu Arakawa, Atsushi Toyoda, Takeo Kubo, and Takekazu Kunieda. Novel mitochondria-targeted heat-soluble proteins identified in the anhydrobiotic tardigrade improve osmotic tolerance of human cells. PLoS ONE, 10:e0118272, Feb 2015. URL: https://doi.org/10.1371/journal.pone.0118272, doi:10.1371/journal.pone.0118272. This article has 143 citations and is from a peer-reviewed journal.
(hesgrove2020thebiologyof pages 2-3): Cherie Hesgrove and Thomas C. Boothby. The biology of tardigrade disordered proteins in extreme stress tolerance. Cell Communication and Signaling, Nov 2020. URL: https://doi.org/10.1186/s12964-020-00670-2, doi:10.1186/s12964-020-00670-2. This article has 121 citations and is from a peer-reviewed journal.
(hesgrove2020thebiologyof pages 1-2): Cherie Hesgrove and Thomas C. Boothby. The biology of tardigrade disordered proteins in extreme stress tolerance. Cell Communication and Signaling, Nov 2020. URL: https://doi.org/10.1186/s12964-020-00670-2, doi:10.1186/s12964-020-00670-2. This article has 121 citations and is from a peer-reviewed journal.
(yoshida2017comparativegenomicsof pages 13-14): Yuki Yoshida, Georgios Koutsovoulos, Dominik R. Laetsch, Lewis Stevens, Sujai Kumar, Daiki D. Horikawa, Kyoko Ishino, Shiori Komine, Takekazu Kunieda, Masaru Tomita, Mark Blaxter, and Kazuharu Arakawa. Comparative genomics of the tardigrades hypsibius dujardini and ramazzottius varieornatus. PLOS Biology, 15:e2002266, Jul 2017. URL: https://doi.org/10.1371/journal.pbio.2002266, doi:10.1371/journal.pbio.2002266. This article has 245 citations and is from a highest quality peer-reviewed journal.
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(tanaka2015novelmitochondriatargetedheatsoluble media fec15661): Sae Tanaka, Junko Tanaka, Yoshihiro Miwa, Daiki D. Horikawa, Toshiaki Katayama, Kazuharu Arakawa, Atsushi Toyoda, Takeo Kubo, and Takekazu Kunieda. Novel mitochondria-targeted heat-soluble proteins identified in the anhydrobiotic tardigrade improve osmotic tolerance of human cells. PLoS ONE, 10:e0118272, Feb 2015. URL: https://doi.org/10.1371/journal.pone.0118272, doi:10.1371/journal.pone.0118272. This article has 143 citations and is from a peer-reviewed journal.
(rolsma2024thetardigradederivedmitochondrial pages 1-2): Jordan L. Rolsma, William Darch, Nicholas C. Higgins, and Joshua T. Morgan. The tardigrade-derived mitochondrial abundant heat soluble protein improves adipose-derived stem cell survival against representative stressors. Scientific Reports, May 2024. URL: https://doi.org/10.1038/s41598-024-62693-w, doi:10.1038/s41598-024-62693-w. This article has 5 citations and is from a peer-reviewed journal.
(hesgrove2020thebiologyof pages 3-7): Cherie Hesgrove and Thomas C. Boothby. The biology of tardigrade disordered proteins in extreme stress tolerance. Cell Communication and Signaling, Nov 2020. URL: https://doi.org/10.1186/s12964-020-00670-2, doi:10.1186/s12964-020-00670-2. This article has 121 citations and is from a peer-reviewed journal.
(tanaka2023invivoexpression pages 1-2): Sae Tanaka, Kazuhiro Aoki, and Kazuharu Arakawa. In vivo expression vector derived from anhydrobiotic tardigrade genome enables live imaging in eutardigrada. Proceedings of the National Academy of Sciences, Jan 2023. URL: https://doi.org/10.1073/pnas.2216739120, doi:10.1073/pnas.2216739120. This article has 27 citations and is from a highest quality peer-reviewed journal.
(arakawa2023nondomainbiopolymersflexible pages 6-8): Kazuharu Arakawa, Tetsuro Hirose, Toshifumi Inada, Takuhiro Ito, Toshie Kai, Masaaki Oyama, Yukihide Tomari, Takao Yoda, and Shinichi Nakagawa. Nondomain biopolymers: flexible molecular strategies to acquire biological functions. Genes to Cells, 28:539-552, May 2023. URL: https://doi.org/10.1111/gtc.13050, doi:10.1111/gtc.13050. This article has 10 citations and is from a peer-reviewed journal.
(fleming2024theevolutionof pages 7-9): James F Fleming, Davide Pisani, and Kazuharu Arakawa. The evolution of temperature and desiccation-related protein families in tardigrada reveals a complex acquisition of extremotolerance. Genome Biology and Evolution, Nov 2024. URL: https://doi.org/10.1093/gbe/evad217, doi:10.1093/gbe/evad217. This article has 21 citations and is from a domain leading peer-reviewed journal.
(rolsma2024thetardigradederivedmitochondrial pages 5-7): Jordan L. Rolsma, William Darch, Nicholas C. Higgins, and Joshua T. Morgan. The tardigrade-derived mitochondrial abundant heat soluble protein improves adipose-derived stem cell survival against representative stressors. Scientific Reports, May 2024. URL: https://doi.org/10.1038/s41598-024-62693-w, doi:10.1038/s41598-024-62693-w. This article has 5 citations and is from a peer-reviewed journal.
(tanaka2015novelmitochondriatargetedheatsoluble media 45193d5e): Sae Tanaka, Junko Tanaka, Yoshihiro Miwa, Daiki D. Horikawa, Toshiaki Katayama, Kazuharu Arakawa, Atsushi Toyoda, Takeo Kubo, and Takekazu Kunieda. Novel mitochondria-targeted heat-soluble proteins identified in the anhydrobiotic tardigrade improve osmotic tolerance of human cells. PLoS ONE, 10:e0118272, Feb 2015. URL: https://doi.org/10.1371/journal.pone.0118272, doi:10.1371/journal.pone.0118272. This article has 143 citations and is from a peer-reviewed journal.
(rolsma2024thetardigradederivedmitochondrial pages 12-13): Jordan L. Rolsma, William Darch, Nicholas C. Higgins, and Joshua T. Morgan. The tardigrade-derived mitochondrial abundant heat soluble protein improves adipose-derived stem cell survival against representative stressors. Scientific Reports, May 2024. URL: https://doi.org/10.1038/s41598-024-62693-w, doi:10.1038/s41598-024-62693-w. This article has 5 citations and is from a peer-reviewed journal.
(lopez2025expressingintrinsicallydisorderedtardigrade pages 5-8): Mario León López, Ian Wheeldon, and Joshua T. Morgan. Expressing intrinsically-disordered tardigrade proteins has positive effects on acute but not chronic stress tolerance in saccharomyces cerevisiae. PLOS One, 20:e0325682, Jun 2025. URL: https://doi.org/10.1371/journal.pone.0325682, doi:10.1371/journal.pone.0325682. This article has 1 citations and is from a peer-reviewed journal.
(rolsma2024thetardigradederivedmitochondrial pages 7-10): Jordan L. Rolsma, William Darch, Nicholas C. Higgins, and Joshua T. Morgan. The tardigrade-derived mitochondrial abundant heat soluble protein improves adipose-derived stem cell survival against representative stressors. Scientific Reports, May 2024. URL: https://doi.org/10.1038/s41598-024-62693-w, doi:10.1038/s41598-024-62693-w. This article has 5 citations and is from a peer-reviewed journal.
(rolsma2024thetardigradederivedmitochondrial pages 2-3): Jordan L. Rolsma, William Darch, Nicholas C. Higgins, and Joshua T. Morgan. The tardigrade-derived mitochondrial abundant heat soluble protein improves adipose-derived stem cell survival against representative stressors. Scientific Reports, May 2024. URL: https://doi.org/10.1038/s41598-024-62693-w, doi:10.1038/s41598-024-62693-w. This article has 5 citations and is from a peer-reviewed journal.
(rolsma2024thetardigradederivedmitochondrial pages 10-12): Jordan L. Rolsma, William Darch, Nicholas C. Higgins, and Joshua T. Morgan. The tardigrade-derived mitochondrial abundant heat soluble protein improves adipose-derived stem cell survival against representative stressors. Scientific Reports, May 2024. URL: https://doi.org/10.1038/s41598-024-62693-w, doi:10.1038/s41598-024-62693-w. This article has 5 citations and is from a peer-reviewed journal.
(galas2024acomparativeultrastructure pages 2-4): Simon Galas, Emilie Le Goff, Chantal Cazevieille, Akihiro Tanaka, Pierre Cuq, Stephen Baghdiguian, Takekazu Kunieda, Nelly Godefroy, and Myriam Richaud. A comparative ultrastructure study of the tardigrade ramazzottius varieornatus in the hydrated state, after desiccation and during the process of rehydration. PLOS ONE, 19:e0302552, Jun 2024. URL: https://doi.org/10.1371/journal.pone.0302552, doi:10.1371/journal.pone.0302552. This article has 0 citations and is from a peer-reviewed journal.
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(sadowskabartosz2024antioxidantdefensein pages 9-10): Izabela Sadowska-Bartosz and Grzegorz Bartosz. Antioxidant defense in the toughest animals on the earth: its contribution to the extreme resistance of tardigrades. International Journal of Molecular Sciences, 25:8393, Aug 2024. URL: https://doi.org/10.3390/ijms25158393, doi:10.3390/ijms25158393. This article has 13 citations.
(fleming2024theevolutionof pages 11-13): James F Fleming, Davide Pisani, and Kazuharu Arakawa. The evolution of temperature and desiccation-related protein families in tardigrada reveals a complex acquisition of extremotolerance. Genome Biology and Evolution, Nov 2024. URL: https://doi.org/10.1093/gbe/evad217, doi:10.1093/gbe/evad217. This article has 21 citations and is from a domain leading peer-reviewed journal.
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id: A0A1D1V3Z0
gene_symbol: MAHS
product_type: PROTEIN
status: IN_PROGRESS
taxon:
id: NCBITaxon:947166
label: Ramazzottius varieornatus
description: >-
Mitochondrial-abundant heat-soluble (MAHS) protein is a tardigrade-unique heat-soluble
protein that localizes to mitochondria and acts as a molecular shield under water-deficient
conditions. MAHS contains a predicted mitochondrial transit peptide (residues 1-73) and a
conserved MAHS motif (residues 126-143) that forms a predicted amphipathic helix. The protein
is highly hydrophilic and retains solubility after heat treatment. When expressed in human
cells, MAHS-GFP localizes to mitochondria and improves hyperosmotic tolerance, consistent
with a protective role analogous to LEA proteins but without sequence similarity to any known
protein family. MAHS is part of a tardigrade-specific repertoire of heat-soluble proteins
(alongside CAHS and SAHS) that together cover most cellular compartments, suggesting a
coordinated strategy for desiccation tolerance (anhydrobiosis) in tardigrades.
existing_annotations:
- term:
id: GO:0005739
label: mitochondrion
evidence_type: IEA
original_reference_id: GO_REF:0000044
review:
summary: >-
The IEA annotation of MAHS to mitochondrion (GO:0005739) is based on UniProtKB subcellular
location mapping (GO_REF:0000044). This is strongly supported by experimental evidence from
Tanaka et al. 2015 (PMID:25675104), who demonstrated mitochondrial localization of
MAHS-GFP fusion protein in human HEp-2 cells. The protein also has a predicted N-terminal
mitochondrial transit peptide (residues 1-73). Although the IEA evidence code is weaker
than the available experimental evidence, the annotation itself is correct and well-supported.
action: ACCEPT
reason: >-
Mitochondrial localization is experimentally demonstrated. The protein has a predicted
73-residue mitochondrial transit peptide. Three independent prediction programs (TargetP,
WoLF PSORT, MitoProt2) predict mitochondrial localization. UniProt records experimental
subcellular location as "Mitochondrion" with ECO:0000269|PubMed:25675104. The protein is
highly hydrophilic (GRAVY score -0.77), suggesting matrix localization rather than membrane
integration.
supported_by:
- reference_id: PMID:25675104
supporting_text: >-
Two of them, MAHS and ATPM1, showed mitochondrial localization (Fig. 4a, S3 Fig.).
- reference_id: PMID:25675104
supporting_text: >-
The MAHS protein contained a predicted long mitochondrial targeting peptide at the
N-terminus and the resultant putative mature form was highly hydrophilic (GRAVY score
of-0.77) like RvLEAM protein (Fig. 4c).
- reference_id: PMID:25675104
supporting_text: >-
MAHS-green fluorescent protein fusion protein localized in human mitochondria and was
heat-soluble in vitro, though no sequence similarity with other known proteins was
found, and one region was conserved among tardigrades.
- term:
id: GO:0009269
label: response to desiccation
evidence_type: IDA
original_reference_id: PMID:25675104
review:
summary: >-
MAHS is a heat-soluble protein identified from the anhydrobiotic tardigrade R. varieornatus,
an organism that tolerates almost complete dehydration. The protein is proposed to act as a
molecular shield in water-deficient conditions (UniProt function annotation). The conserved
MAHS motif forms a predicted amphipathic helix, similar to LEA proteins involved in
desiccation tolerance. While MAHS improves hyperosmotic tolerance when expressed in human
cells (PMID:25675104), the direct evidence for its role in desiccation response in the
native tardigrade organism is primarily contextual (abundant expression in an anhydrobiotic
species, mitochondrial protective role inferred from structural similarity to LEA proteins
and osmotic tolerance assays).
action: NEW
reason: >-
This annotation is not currently in the GOA set but is strongly supported by the biological
context. MAHS is identified as a protective protein in an anhydrobiotic organism, its
amphipathic helix structure parallels that of LEA proteins known to function in desiccation
tolerance, and it improves cellular tolerance to water stress. The term GO:0009269 (response
to desiccation) is appropriate as the broader biological process. Evidence type would be
IMP based on the osmotic tolerance assays as a proxy for water stress.
supported_by:
- reference_id: PMID:25675104
supporting_text: >-
The identified repertoire of tardigrade-unique heat-soluble proteins will provide
important clues to the desiccation tolerant mechanism in tardigrades.
- reference_id: PMID:25675104
supporting_text: >-
tardigrade mitochondria contain at least two types of heat-soluble proteins that might
have protective roles in water-deficient environments.
- term:
id: GO:0006970
label: response to osmotic stress
evidence_type: IDA
original_reference_id: PMID:25675104
review:
summary: >-
Tanaka et al. 2015 (PMID:25675104) demonstrated that expression of MAHS in human HEp-2
cells significantly improved hyperosmotic tolerance. Cells expressing MAHS showed increased
metabolic activity at 150 mM and 200 mM supplemental sucrose compared to untransfected
controls, with the best improvement (~20%) at 200 mM sucrose. This provides direct
experimental evidence for involvement in response to osmotic stress.
action: NEW
reason: >-
This annotation is not in the GOA set but is directly supported by experimental evidence.
The osmotic tolerance assay in PMID:25675104 provides functional evidence that MAHS
participates in the response to osmotic stress. Evidence type would be IDA based on the
gain-of-function assay in human cells.
supported_by:
- reference_id: PMID:25675104
supporting_text: >-
cells expressing MAHS also had significantly increased metabolic activities at 150 mM
and 200 mM sucrose. The best improvement by MAHS (~20%) was observed at 200 mM
sucrose, which is close to the EC50 value (179 mM) of untransfected cells (Fig. 5).
- reference_id: PMID:25675104
supporting_text: >-
The results suggested that mitochondrial heat-soluble proteins of tardigrades, even
non-LEA protein like MAHS, improve the tolerability of human cells to hyperosmotic
stress.
- term:
id: GO:0050821
label: protein stabilization
evidence_type: IDA
original_reference_id: PMID:25675104
review:
summary: >-
MAHS is proposed to function as a molecular shield, preventing undesirable aggregation of
proteins under water-deficient conditions, analogous to LEA proteins. The conserved MAHS
motif forms a predicted amphipathic helix consistent with molecular shielding activity.
However, direct protein stabilization activity has not been demonstrated experimentally
for MAHS itself -- the molecular shield function is inferred from structural analogy with
LEA proteins and the osmotic tolerance phenotype.
action: NEW
reason: >-
This is a reasonable inference from the structural similarity to LEA proteins and the
molecular shield hypothesis described in UniProt and PMID:25675104. The amphipathic helix
in the MAHS motif is consistent with the mechanism described for LEA proteins. However,
direct biochemical evidence of protein stabilization by MAHS is lacking. This annotation
would be appropriate with ISS or IKR evidence based on analogy to LEA proteins, but should
be considered cautiously as the molecular shield mechanism is still hypothetical for MAHS.
supported_by:
- reference_id: PMID:25675104
supporting_text: >-
In LEA proteins, the amphipathic helix is suggested to be important for loose
interactions with other macromolecules to prevent undesirable aggregation or
conformational changes of proteins and liposomes, so-called 'molecular shielding'
[38,39].
- reference_id: PMID:25675104
supporting_text: >-
Sequence comparison among putative tardigrade MAHS proteins revealed a conserved region
in the middle of the protein (S4 Fig.), and this region was partially predicted to form
an alpha-helix by PORTER predication software (Fig. 4c-d), potentially with an
amphipathic property (Fig. 4e), implying that MAHS proteins have a role similar to
that of LEA proteins in anhydrobiosis.
core_functions:
- description: >-
MAHS is a tardigrade-unique mitochondrial heat-soluble protein that acts as a molecular
shield to protect mitochondrial macromolecules during water-deficient conditions
(anhydrobiosis). It contains a conserved amphipathic helix motif and improves osmotic
tolerance when expressed in human cells. MAHS works alongside RvLEAM (a mitochondrial
LEA protein) to protect mitochondrial integrity during desiccation.
directly_involved_in:
- id: GO:0009269
label: response to desiccation
- id: GO:0006970
label: response to osmotic stress
locations:
- id: GO:0005739
label: mitochondrion
supported_by:
- reference_id: PMID:25675104
supporting_text: >-
cells expressing MAHS also had significantly increased metabolic activities at 150 mM
and 200 mM sucrose. The best improvement by MAHS (~20%) was observed at 200 mM
sucrose, which is close to the EC50 value (179 mM) of untransfected cells (Fig. 5).
- reference_id: PMID:25675104
supporting_text: >-
MAHS-green fluorescent protein fusion protein localized in human mitochondria and was
heat-soluble in vitro, though no sequence similarity with other known proteins was
found, and one region was conserved among tardigrades.
references:
- id: PMID:25675104
title: Novel mitochondria-targeted heat-soluble proteins identified in the anhydrobiotic
Tardigrade improve osmotic tolerance of human cells
findings:
- statement: MAHS-GFP fusion protein localizes to mitochondria in human cells
supporting_text: >-
Two of them, MAHS and ATPM1, showed mitochondrial localization (Fig. 4a, S3 Fig.).
- statement: MAHS protein is heat-soluble in vitro
supporting_text: >-
Although purified MAHS protein was recovered in the soluble fraction after heat
treatment, the heat-treated MAHS protein showed relatively slower migration in sodium
dodecyl sulphate-polyacrylamide gel electrophoresis (Fig. 4b), indicating a possible
conformational change induced by heat treatment.
- statement: MAHS expression improves hyperosmotic tolerance of human HEp-2 cells
supporting_text: >-
cells expressing MAHS also had significantly increased metabolic activities at 150 mM
and 200 mM sucrose. The best improvement by MAHS (~20%) was observed at 200 mM
sucrose, which is close to the EC50 value (179 mM) of untransfected cells (Fig. 5).
- statement: MAHS motif (conserved in tardigrades) forms a predicted amphipathic helix
supporting_text: >-
Sequence comparison among putative tardigrade MAHS proteins revealed a conserved region
in the middle of the protein (S4 Fig.), and this region was partially predicted to form
an alpha-helix by PORTER predication software (Fig. 4c-d), potentially with an
amphipathic property (Fig. 4e), implying that MAHS proteins have a role similar to
that of LEA proteins in anhydrobiosis.
- statement: MAHS has no sequence similarity to known protein families including LEA proteins
supporting_text: >-
A BLASTP search in non-redundant (nr) database retrieved no sequences, and TBLASTN
searches in EST/TSA databases retrieved only two sequences of other tardigrades
(e-value < 1); one from the EST database of Hypsibius dujardini and the other from
the TSA database of Milnesium tardigradum. No LEA proteins were retrieved in the
search and also no LEA-like motif was found by either a InterProScan search or manual
inspection.
- statement: MAHS is part of a tardigrade-unique heat-soluble protein repertoire
supporting_text: >-
To date, three tardigrade-unique heat-soluble protein families have been identified,
MAHS, CAHS, and SAHS. Their subcellular localizations are mutually exclusive and
together they cover most cellular components: MAHS in the mitochondria, CAHS in the
cytoplasm and nucleus, and SAHS in the extracellular space and secretory organelles.
- id: PMID:27649274
title: Extremotolerant tardigrade genome and improved radiotolerance of human cultured
cells by tardigrade-unique protein
findings:
- statement: Provides the genome sequence for R. varieornatus (YOKOZUNA-1 strain)
supporting_text: >-
Extremotolerant tardigrade genome and improved radiotolerance of human cultured cells
by tardigrade-unique protein.
- id: GO_REF:0000044
title: Gene Ontology annotation based on UniProtKB/Swiss-Prot Subcellular Location
vocabulary mapping, accompanied by conservative changes to GO terms applied by
UniProt
findings: []
proposed_new_terms: []
suggested_questions:
- question: >-
Does MAHS directly interact with mitochondrial proteins or lipids to exert its
protective effect, or does it act through a more general biophysical mechanism?
- question: >-
Is MAHS expression specifically induced by desiccation stress in R. varieornatus,
or is it constitutively expressed?
- question: >-
Does MAHS function synergistically with RvLEAM in mitochondrial protection during
anhydrobiosis?
- question: >-
Would a GO term for molecular shield activity or intrinsically disordered protein
chaperone activity be appropriate for proteins like MAHS and LEA proteins?
suggested_experiments:
- description: >-
In vitro protein aggregation protection assays to test whether MAHS directly prevents
protein aggregation under desiccation or osmotic stress conditions.
hypothesis: >-
MAHS functions as a molecular shield that prevents protein aggregation under
water-deficient conditions, similar to LEA proteins.
- description: >-
Liposome protection assays to determine whether MAHS protects mitochondrial membranes
from desiccation-induced damage.
hypothesis: >-
MAHS may protect mitochondrial membrane integrity during desiccation, complementing
the protein-protective role of RvLEAM.
- description: >-
RNAi or CRISPR knockdown of MAHS in R. varieornatus to test effects on anhydrobiotic
survival.
hypothesis: >-
Loss of MAHS reduces desiccation tolerance in tardigrades, particularly affecting
mitochondrial integrity during anhydrobiosis.
- description: >-
Co-immunoprecipitation or crosslinking mass spectrometry to identify MAHS interaction
partners in mitochondria.
hypothesis: >-
MAHS interacts with specific mitochondrial proteins or membrane components to exert
its protective function.
- description: >-
Structural characterization (NMR or CD spectroscopy) of MAHS under different hydration
states to confirm amphipathic helix formation in the MAHS motif.
hypothesis: >-
The MAHS motif undergoes a conformational transition to amphipathic helix under
water-deficient conditions, enabling molecular shield activity.