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this with annotations you find in gene/protein databases, but these can be outdated or inaccurate.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 evidence base used here is consistent with the UniProt-provided identity: human PEX7 encodes the peroxisomal targeting signal 2 (PTS2) receptor (peroxin-7), a WD40-repeat β-propeller protein required for the PTS2 peroxisomal matrix protein import pathway. Multiple sources explicitly define PEX7/Pex7 as the receptor for PTS2-containing matrix proteins, note its WD40 seven-bladed propeller architecture, and describe its requirement for the human co-receptor PEX5L. (rudowitz2023importandquality pages 2-3, ghosh2023dynamicsofthe pages 1-2, ghosh2024molecularcharacterizationof pages 19-22)
| Topic | Summary Statement | Evidence | Source |
|---|---|---|---|
| Identity & Structure | Human PEX7 (UniProt O00628) is the cytosolic receptor for peroxisomal matrix proteins carrying a Type 2 targeting signal (PTS2). It belongs to the WD40 repeat family, forming a seven-bladed $\beta$-propeller structure essential for ligand binding. | (lipinski2025earlystagesof pages 16-19, ghosh2024molecularcharacterizationof pages 19-22, rudowitz2023importandquality pages 2-3) | Rudowitz et al., 2023; Lipiński, 2025; Ghosh, 2024 |
| Targeting Signal | Recognizes the N-terminal PTS2 nonapeptide motif with the consensus [R/K][L/I/V/Q]X2[L/I/V/H/Q][L/S/G/A/K]X[H/Q][L/A/F]. Binding triggers conformational changes facilitating import. |
(lipinski2025earlystagesof pages 16-19, rudowitz2023importandquality pages 2-3) | Rudowitz et al., 2023; Lipiński, 2025 |
| Co-receptor Mechanism | PEX7 cannot drive import alone; in humans, it requires the long isoform of PEX5 (PEX5L) as a co-receptor. PEX5L contains a specific 37-residue epitope (approx. residues 191–222) that binds PEX7, forming a stable cargo-receptor complex. | (ghosh2024molecularcharacterizationof pages 19-22, rudowitz2023importandquality pages 2-3, ghosh2023dynamicsofthe pages 1-2, lipinski2025earlystagesofa pages 16-19) | Ghosh et al., 2023; Rudowitz et al., 2023; Ghosh, 2024 |
| Docking & Translocation | The PEX7-PEX5L-cargo complex docks at the peroxisomal membrane via interactions with PEX13 and PEX14. PEX5L integration into the membrane is linked to the formation of a dynamic, gated translocation pore (diameter ~0.6 nm resting to ~9 nm active). | (rudowitz2023importandquality pages 2-3, ghosh2023dynamicsofthe pages 1-2, ghosh2023dynamicsofthe pages 5-7, ghosh2024molecularcharacterizationof pages 25-28) | Ghosh et al., 2023; Rudowitz et al., 2023; Ghosh, 2024 |
| Key Cargos | Canonical cargos include AGPS (plasmalogen biosynthesis), PHYH (phytanic acid oxidation), and ACAA1 (fatty acid beta-oxidation). Pathogenic PEX7 variants cause deficiency in these enzymes. | (braverman2020rhizomelicchondrodysplasiapunctata pages 19-22, gerami2023antenatalultrasonographicdiagnosis pages 1-2, braverman2020rhizomelicchondrodysplasiapunctata pages 13-15) | Braverman et al., 2020; Gerami et al., 2023 |
| Recent Novel Cargo (2024) | HMG-CoA Reductase (HMGCR): Under low sterol/statin conditions, a truncated soluble fragment of HMGCR is imported into peroxisomes via a PEX7/PTS2-dependent mechanism to support cholesterol synthesis. | (braverman2020rhizomelicchondrodysplasiapunctata pages 19-22, wang2024peroxisomallocalizationof pages 2-3, wang2024peroxisomallocalizationof pages 1-2) | Wang et al., 2024 |
| Disease Association | Biallelic PEX7 mutations cause Rhizomelic Chondrodysplasia Punctata Type 1 (RCDP1). Classic features: rhizomelia, punctate calcifications, cataracts, severe intellectual disability, and early mortality. | (braverman2020rhizomelicchondrodysplasiapunctata pages 1-3, braverman2020rhizomelicchondrodysplasiapunctata pages 3-8, braverman2020rhizomelicchondrodysplasiapunctata pages 8-10) | Braverman et al., 2020; Gerami et al., 2023 |
| Biochemical Hallmarks | RCDP1 is characterized by profound plasmalogen deficiency in erythrocytes (severity correlates with levels) and elevated plasma phytanic acid. VLCFA levels are typically normal. | (braverman2020rhizomelicchondrodysplasiapunctata pages 1-3, braverman2020rhizomelicchondrodysplasiapunctata pages 19-22, braverman2020rhizomelicchondrodysplasiapunctata pages 13-15) | Braverman et al., 2020 |
| Quantitative Data | In differentiated THP-1 cells and primary macrophages, ~65-68% of truncated HMGCR localizes to peroxisomes under lipid depletion; this localization is abolished in PEX7-deficient RCDP1 fibroblasts. | (wang2024peroxisomallocalizationof pages 2-3, wang2024peroxisomallocalizationof media c7ce012e) | Wang et al., 2024 |
Table: This table summarizes the primary function, molecular mechanisms, cargo specificity, and disease relevance of human PEX7, integrating established knowledge with recent findings from 2023-2024 literature regarding its role in cholesterol metabolism.
Peroxisomal matrix proteins are synthesized in the cytosol and imported post-translationally, often in a folded state, using targeting signals and cycling receptors. (ghosh2023dynamicsofthe pages 1-2)
PTS1 vs PTS2
- PTS1: a targeting signal recognized by PEX5/PEX5L (the principal PTS1 receptor). (ghosh2023dynamicsofthe pages 1-2)
- PTS2: an N-terminal nonapeptide signal recognized by PEX7. A consensus motif for PTS2 has been described (e.g., [R/K][L/I/V/Q]X2[L/I/V/H/Q][L/S/G/A/K]X[H/Q][L/A/F]). (rudowitz2023importandquality pages 2-3)
Primary function: PEX7 is the cytosolic receptor that binds PTS2-containing peroxisomal matrix proteins, enabling their delivery to the peroxisome for import into the matrix. (rudowitz2023importandquality pages 2-3, ghosh2023dynamicsofthe pages 1-2)
PEX7 is not an enzyme; it is a cargo-recognition and trafficking factor (a “peroxin”) whose substrate specificity is defined by recognition of the PTS2 targeting motif on cargo proteins. (rudowitz2023importandquality pages 2-3)
PEX7 is described as a WD40-repeat protein forming a seven-bladed β-propeller, consistent with a scaffolding/ligand-binding role. (rudowitz2023importandquality pages 2-3)
A key mechanistic point is that PEX7 cannot drive import alone and requires a co-receptor. In humans, the long isoform PEX5L is the PTS2 co-receptor, so PTS1 and PTS2 pathways converge downstream at PEX5/PEX5L-mediated steps. (rudowitz2023importandquality pages 2-3, ghosh2023dynamicsofthe pages 1-2)
PEX7 is a cytosolic receptor that binds PTS2 cargos in the cytosol and participates in their targeting to the peroxisomal membrane import machinery. (rudowitz2023importandquality pages 2-3, ghosh2023dynamicsofthe pages 1-2)
A consolidated import cycle supported by recent review/primary literature is:
1. Cargo recognition in cytosol: PEX7 binds PTS2-bearing cargo, together with its co-receptor PEX5L in humans. (rudowitz2023importandquality pages 2-3, ghosh2023dynamicsofthe pages 1-2)
2. Docking at the peroxisomal membrane: receptor–cargo complexes dock via interactions with PEX13/PEX14 (docking complex). (ghosh2023dynamicsofthe pages 1-2, rudowitz2023importandquality pages 2-3)
3. Translocation through a dynamic pore: PEX5/PEX5L becomes part of an import complex; a transient, gated pore can form to allow translocation of folded proteins. (ghosh2023dynamicsofthe pages 1-2, ghosh2023dynamicsofthe pages 5-7)
4. Cargo release: cargo is released into the matrix (mechanistic details remain actively studied). (ghosh2023dynamicsofthe pages 1-2)
5. Receptor recycling: receptor components are ubiquitinated and extracted back to the cytosol by AAA ATPases (PEX1/PEX6/PEX26), enabling repeated rounds of import. (ghosh2023dynamicsofthe pages 1-2)
A 2023 study reconstituted purified human PEX5L-containing complexes into planar lipid membranes and observed water-filled pores with dynamic conductance states and cargo/receptor-complex sensitivity, supporting a model in which receptor complexes can constitute a translocation pore. Because human PTS2 import requires PEX5L as co-receptor for PEX7, these data are relevant to the PEX7-dependent pathway downstream convergence and mechanistic understanding of import. (ghosh2023dynamicsofthe pages 1-2, ghosh2023dynamicsofthe pages 5-7)
A clinical genetics review on PEX7-RCDP states that PEX7 (PTS2 receptor) imports multiple PTS2-targeted enzymes, including:
- AGPS (alkylglycerone phosphate synthase; required for plasmalogen/ether lipid synthesis),
- PHYH (phytanoyl-CoA 2-hydroxylase; required for phytanic acid oxidation), and
- ACAA1 (peroxisomal 3-ketoacyl-CoA thiolase; peroxisomal fatty acid metabolism). (braverman2020rhizomelicchondrodysplasiapunctata pages 19-22)
These cargos connect PEX7 function to two hallmark peroxisomal metabolic outputs: ether lipid (plasmalogen) biosynthesis and α-oxidation of phytanic acid. (braverman2020rhizomelicchondrodysplasiapunctata pages 19-22)
PEX7-related rhizomelic chondrodysplasia punctata (RCDP1) is an autosomal recessive peroxisome biogenesis disorder caused by biallelic pathogenic variants in PEX7. (braverman2020rhizomelicchondrodysplasiapunctata pages 1-3, braverman2020rhizomelicchondrodysplasiapunctata pages 19-22)
Classic (severe) RCDP1 is characterized by rhizomelia (proximal limb shortening), chondrodysplasia punctata (epiphyseal stippling), vertebral coronal clefts, and cataracts often present at birth or early infancy, with profound growth and neurodevelopmental impairment and frequent seizures. (braverman2020rhizomelicchondrodysplasiapunctata pages 1-3, braverman2020rhizomelicchondrodysplasiapunctata pages 8-10)
A key biochemical signature is marked deficiency of plasmalogens in red blood cells with severity correlation, and elevated plasma phytanic acid (especially after dietary exposure), while very-long-chain fatty acids (VLCFA) are typically normal, consistent with selective loss of specific PTS2 enzyme activities rather than global peroxisome absence. (braverman2020rhizomelicchondrodysplasiapunctata pages 1-3)
Mechanistically, disease is attributed to disrupted PTS2 import causing deficient activity of specific PTS2 enzymes (including AGPS and PHYH), while PTS1 import can remain intact. (braverman2020rhizomelicchondrodysplasiapunctata pages 19-22)
Cohort survival data summarized in the PEX7-RCDP review indicate severe outcomes in classic disease. One series reported survival of ~90% at 1 year, declining to ~55% by 5 years and ~20% by 12 years; another series reported 80% to age 5, 45% to age 12, and 35% to adulthood, with deaths commonly due to respiratory complications. (braverman2020rhizomelicchondrodysplasiapunctata pages 3-8)
The same review describes RCDP1 as very rare (reported as <1:100,000, with an estimate of 0.5 per 100,000 births) and notes approximately ~190 living affected individuals in the U.S. (braverman2020rhizomelicchondrodysplasiapunctata pages 10-13)
Genotype–phenotype correlations summarized include:
- p.Leu292Ter: commonly associated with classic (severe) disease when homozygous; described as a common founder allele. (braverman2020rhizomelicchondrodysplasiapunctata pages 10-13, braverman2020rhizomelicchondrodysplasiapunctata pages 22-23)
- p.His285Arg: described as a frequent hypomorphic allele associated with milder phenotypes and suggested as a Dutch founder variant. (braverman2020rhizomelicchondrodysplasiapunctata pages 10-13)
The review also emphasizes that “leaky” alleles (including some 5′UTR/intronic and frameshift contexts permitting reinitiation) can be associated with milder/nonclassic RCDP or adult Refsum disease-like phenotypes. (braverman2020rhizomelicchondrodysplasiapunctata pages 22-23)
Clinical and laboratory testing
- Diagnosis is established by suggestive clinical/radiographic features plus biallelic pathogenic variants in PEX7. (braverman2020rhizomelicchondrodysplasiapunctata pages 3-8)
- Molecular diagnostic yield: sequence analysis of coding and flanking intronic regions identified ~97% of pathogenic variants in a cohort of 133 individuals. (braverman2020rhizomelicchondrodysplasiapunctata pages 3-8)
- Biochemical testing includes RBC plasmalogen quantification (e.g., by GC-MS; LC-MS/MS approaches are also discussed as diagnostically useful). (braverman2020rhizomelicchondrodysplasiapunctata pages 1-3, braverman2020rhizomelicchondrodysplasiapunctata pages 3-8)
Prenatal diagnosis
A 2023 ultrasound case report highlights prenatal detection (rhizomelia + epiphyseal stippling) followed by invasive testing and PEX7 molecular confirmation; it also states that RCDP type 1 comprises >90% of reported RCDP cases. (gerami2023antenatalultrasonographicdiagnosis pages 1-2)
A 2024 study reports a new PEX7-dependent phenomenon: under sterol-depleted and statin-treated conditions, a truncated soluble catalytic domain of HMG-CoA reductase (HMGCR) shows dual localization to ER and peroxisomes, and peroxisomal localization depends on PEX7-mediated PTS2 import. Peroxisomal HMGCR localization was absent in fibroblasts from RCDP1 patients lacking functional PEX7, and a PTS2-like motif was shown functional in a reporter context. (wang2024peroxisomallocalizationof pages 1-2)
Quantitative data (Table 1): the study quantified peroxisomal HMGCR fractions in cell types under treatment; for example, differentiated THP-1 cells and primary macrophages showed high peroxisomal localization fractions (up to ~68% and 65%, respectively). (wang2024peroxisomallocalizationof media c7ce012e)
PEX7 is implemented clinically as a diagnostic gene in peroxisome biogenesis disorder workups, particularly for RCDP1, supported by established biochemical tests (RBC plasmalogens; phytanic acid) and confirmatory sequencing. (braverman2020rhizomelicchondrodysplasiapunctata pages 1-3, braverman2020rhizomelicchondrodysplasiapunctata pages 3-8)
Prenatal ultrasound patterns (rhizomelia and stippled epiphyses) are used in practice to trigger confirmatory molecular testing (including PEX7) and counseling for autosomal recessive recurrence risk. (gerami2023antenatalultrasonographicdiagnosis pages 1-2)
The 2024 evidence that HMGCR fragments can be PEX7/PTS2-imported under cholesterol depletion suggests peroxisomal import pathways may contribute to context-dependent redistribution of metabolic enzymes during sterol stress, with potential implications for understanding statin responses and peroxisome–ER metabolic coordination. This remains an emerging area rather than established clinical practice. (wang2024peroxisomallocalizationof pages 1-2, wang2024peroxisomallocalizationof media c7ce012e)
Two authoritative, mechanistically focused sources (a 2023 Journal of Cell Science review and a 2023 Biological Chemistry primary study) support a contemporary view that peroxisomal import can proceed through dynamic, receptor-associated translocation machinery and that PEX7-mediated PTS2 import requires PEX5L in humans, emphasizing convergence of PTS1/PTS2 systems at shared downstream steps. (rudowitz2023importandquality pages 2-3, ghosh2023dynamicsofthe pages 1-2)
On the clinical side, a comprehensive RCDP1 review synthesizes genotype–phenotype, prognosis, and biochemical hallmarks, emphasizing that PEX7 mutations specifically disrupt import of PTS2 enzymes (AGPS/PHYH/ACAA1) and that RBC plasmalogen levels are a key biomarker tied to clinical severity. (braverman2020rhizomelicchondrodysplasiapunctata pages 1-3, braverman2020rhizomelicchondrodysplasiapunctata pages 19-22)
Human PEX7 (O00628) is a WD40 β-propeller cytosolic receptor that recognizes N-terminal PTS2 signals on a restricted set of peroxisomal matrix proteins and, with the PEX5L co-receptor, docks at the PEX13/PEX14 import machinery to enable translocation into the peroxisome matrix and subsequent receptor recycling by ubiquitination/AAA ATPases. (rudowitz2023importandquality pages 2-3, ghosh2023dynamicsofthe pages 1-2)
Clinically, biallelic loss-of-function variants cause RCDP1, with characteristic skeletal, ocular, neurologic phenotype, plasmalogen deficiency, and poor survival in classic disease; severity correlates with plasmalogen levels and specific alleles. (braverman2020rhizomelicchondrodysplasiapunctata pages 1-3, braverman2020rhizomelicchondrodysplasiapunctata pages 3-8)
Recent research (2023–2024) advances mechanistic understanding of the dynamic import pore and broadens the landscape of potential PEX7-dependent peroxisomal cargo under metabolic stress (HMGCR fragment import under sterol depletion/statin exposure). (ghosh2023dynamicsofthe pages 1-2, wang2024peroxisomallocalizationof pages 1-2)
References
(rudowitz2023importandquality pages 2-3): Markus Rudowitz and Ralf Erdmann. Import and quality control of peroxisomal proteins. Journal of cell science, Aug 2023. URL: https://doi.org/10.1242/jcs.260999, doi:10.1242/jcs.260999. This article has 16 citations and is from a domain leading peer-reviewed journal.
(ghosh2023dynamicsofthe pages 1-2): Mausumi Ghosh, Niels Denkert, Maren Reuter, Jessica Klümper, Katharina Reglinski, Rebecca Peschel, Wolfgang Schliebs, Ralf Erdmann, and Michael Meinecke. Dynamics of the translocation pore of the human peroxisomal protein import machinery. Biological Chemistry, 404:169-178, Aug 2023. URL: https://doi.org/10.1515/hsz-2022-0170, doi:10.1515/hsz-2022-0170. This article has 10 citations and is from a peer-reviewed journal.
(ghosh2024molecularcharacterizationof pages 19-22): Mausumi Ghosh. Molecular characterization of protein translocation pores. ArXiv, 2024. URL: https://doi.org/10.53846/goediss-10355, doi:10.53846/goediss-10355. This article has 0 citations.
(lipinski2025earlystagesof pages 16-19): O Lipiński. Early stages of peroxisomal protein import. Unknown journal, 2025.
(lipinski2025earlystagesofa pages 16-19): O Lipiński. Early stages of peroxisomal protein import. Unknown journal, 2025.
(ghosh2023dynamicsofthe pages 5-7): Mausumi Ghosh, Niels Denkert, Maren Reuter, Jessica Klümper, Katharina Reglinski, Rebecca Peschel, Wolfgang Schliebs, Ralf Erdmann, and Michael Meinecke. Dynamics of the translocation pore of the human peroxisomal protein import machinery. Biological Chemistry, 404:169-178, Aug 2023. URL: https://doi.org/10.1515/hsz-2022-0170, doi:10.1515/hsz-2022-0170. This article has 10 citations and is from a peer-reviewed journal.
(ghosh2024molecularcharacterizationof pages 25-28): Mausumi Ghosh. Molecular characterization of protein translocation pores. ArXiv, 2024. URL: https://doi.org/10.53846/goediss-10355, doi:10.53846/goediss-10355. This article has 0 citations.
(braverman2020rhizomelicchondrodysplasiapunctata pages 19-22): NE Braverman, SJ Steinberg, and W Fallatah. Rhizomelic chondrodysplasia punctata type 1. Unknown journal, 2020.
(gerami2023antenatalultrasonographicdiagnosis pages 1-2): Reza Gerami and Shoresh Barkhordari. Antenatal ultrasonographic diagnosis of rhizomelic chondrodysplasia punctata. Journal of Ultrasound, 26:539-542, Oct 2023. URL: https://doi.org/10.1007/s40477-022-00737-5, doi:10.1007/s40477-022-00737-5. This article has 6 citations.
(braverman2020rhizomelicchondrodysplasiapunctata pages 13-15): NE Braverman, SJ Steinberg, and W Fallatah. Rhizomelic chondrodysplasia punctata type 1. Unknown journal, 2020.
(wang2024peroxisomallocalizationof pages 2-3): Jianqiu Wang, Markus Kunze, Andrea Villoria-González, Isabelle Weinhofer, and Johannes Berger. Peroxisomal localization of a truncated hmg-coa reductase under low cholesterol conditions. Feb 2024. URL: https://doi.org/10.3390/biom14020244, doi:10.3390/biom14020244. This article has 7 citations.
(wang2024peroxisomallocalizationof pages 1-2): Jianqiu Wang, Markus Kunze, Andrea Villoria-González, Isabelle Weinhofer, and Johannes Berger. Peroxisomal localization of a truncated hmg-coa reductase under low cholesterol conditions. Feb 2024. URL: https://doi.org/10.3390/biom14020244, doi:10.3390/biom14020244. This article has 7 citations.
(braverman2020rhizomelicchondrodysplasiapunctata pages 1-3): NE Braverman, SJ Steinberg, and W Fallatah. Rhizomelic chondrodysplasia punctata type 1. Unknown journal, 2020.
(braverman2020rhizomelicchondrodysplasiapunctata pages 3-8): NE Braverman, SJ Steinberg, and W Fallatah. Rhizomelic chondrodysplasia punctata type 1. Unknown journal, 2020.
(braverman2020rhizomelicchondrodysplasiapunctata pages 8-10): NE Braverman, SJ Steinberg, and W Fallatah. Rhizomelic chondrodysplasia punctata type 1. Unknown journal, 2020.
(wang2024peroxisomallocalizationof media c7ce012e): Jianqiu Wang, Markus Kunze, Andrea Villoria-González, Isabelle Weinhofer, and Johannes Berger. Peroxisomal localization of a truncated hmg-coa reductase under low cholesterol conditions. Feb 2024. URL: https://doi.org/10.3390/biom14020244, doi:10.3390/biom14020244. This article has 7 citations.
(braverman2020rhizomelicchondrodysplasiapunctata pages 10-13): NE Braverman, SJ Steinberg, and W Fallatah. Rhizomelic chondrodysplasia punctata type 1. Unknown journal, 2020.
(braverman2020rhizomelicchondrodysplasiapunctata pages 22-23): NE Braverman, SJ Steinberg, and W Fallatah. Rhizomelic chondrodysplasia punctata type 1. Unknown journal, 2020.