Evolution of high-molecular-mass hyaluronic acid is associated with subterranean lifestyle.
-
Naked mole rat HYAL2 was cloned and expressed, and a naked-mole-rat/Damaraland-mole-rat-specific substitution at residue 284 in the catalytic GH domain was shown to weaken, but not abolish, its hyaluronan-degrading activity.
"A positively selected site G284 was also identified in NMR and DMR HYAL2 (Fig. 3c). We tested the effect of this mutation on NMR HYAL2. We did not observe difference when HA was incubated for two days, but the size and amount of HA was smaller after three days of incubation (Fig. 5i), suggesting that the substitution in G284 also contributes to the weaker HYAL2 in NMRs."
-
Naked mole rat HYAL2 transcript is not reduced relative to control species in skin fibroblasts or kidney.
"NMR had a higher expression of HYAL2 and a drastically lower expression of HYAL1 in the kidney"
High-molecular-mass hyaluronan mediates the cancer resistance of the naked mole rat.
-
Naked mole rat cells and tissues have markedly lower bulk hyaluronidase activity than human, mouse or guinea pig, so both increased synthesis and slowed degradation contribute to high-molecular-mass hyaluronan accumulation.
"HAase activity of the naked mole-rat cells was much lower than that of human, mouse or guinea pig cells (Figure 2c). Similarly, HAase activity was lower in the naked mole-rat tissues than in the mouse tissues (Figure 2d). These results indicate that two mechanisms contribute to accumulation of HMW-HA in the naked mole-rat: more robust synthesis and slower degradation."
-
The Hyal2 overexpression construct used to abolish the cancer-resistance phenotype was the HUMAN HYAL2 cDNA, so those experiments carry no information about the catalytic properties or physiological role of the naked mole rat protein.
"Human Hyal2 cDNA was amplified from pCMV6-HYAL2 (sc117754 OriGene)"
Abundance and size of hyaluronan in naked mole-rat tissues and plasma.
-
RNAseq argues against markedly reduced Hyal2 transcription in the naked mole rat, and the authors state that the isoenzyme responsible for the reduced hyaluronidase activity has never been resolved.
"The RNAseq data obtained in our study seem to rule out a markedly decreased transcription of the Hyal2 gene, but we have no information about NMR lymph node HYAL2 activity."
-
HYAL2 is the GPI-linked cell-surface enzyme that performs the first step of somatic hyaluronan depolymerisation, upstream of lysosomal HYAL1.
"The principal somatic HA-depolymerizing enzymes, i.e. hyaluronidases, are HYAL1 and HYAL2. HA is degraded at the cell surface by the glycosylphosphatidylinositol (GPI)-linked HYAL2 into intermediate-size fragments."
Naked mole-rat TMEM2 lacks physiological hyaluronan-degrading activity.
-
The naked mole rat ortholog of TMEM2, a structurally unrelated cell-surface hyaluronidase, is catalytically inactive, offering an alternative explanation for the reduced hyaluronan degradation in this species.
"Thus, unlike mTMEM2, nmrTMEM2 is not a physiological hyaluronidase. The inability of nmrTMEM2 to degrade HA might partially account for the high-molecular-weight HA accumulation in NMR tissues."
Naked mole-rat very-high-molecular-mass hyaluronan exhibits superior cytoprotective properties.
-
Hyaluronan polymer length, not merely abundance, determines the biological outcome, with very-high-molecular-mass and shorter high-molecular-mass hyaluronan having opposing effects through CD44.
"vHMM-HA (>6.1 MDa) has superior cytoprotective properties compared to the shorter HMM-HA."
Amino acid residues that are important for Hyal2 function as a receptor for jaagsiekte sheep retrovirus.
-
Mouse Hyal2 neither binds jaagsiekte sheep retrovirus Env nor mediates entry, and shows 1,000-fold lower receptor activity than human Hyal2; GOA records this as an explicit NOT|enables GO:0001618 annotation on mouse Hyal2.
"Human Hyal2 binds the envelope (Env) proteins of these viruses and is functional as a receptor, but Hyal2 from mice does not bind Env nor does it mediate entry of either virus."
-
Receptor competence is determined by multiple co-acting residues in the central third of the protein, so it cannot be predicted from any single residue in an untested ortholog.
"None of the single or double mutation reduced the receptor activity of human Hyal2 by more than 10-fold, whereas mouse Hyal2 activity is reduced 1,000-fold from that of human Hyal2."
Transforming growth factor beta1 signaling via interaction with cell surface Hyal-2 and recruitment of WWOX/WOX1.
-
Cell-surface Hyal-2 binds TGF-beta1 on microvilli and recruits WWOX/WOX1, with the complex reported to relocate to the nucleus and enhance Smad-driven promoter activity.
"we determined that TGF-beta1 bound cell surface hyaluronidase Hyal-2 on microvilli in type II TGF-beta receptor-deficient HCT116 cells, as determined by immunoelectron microscopy. This binding resulted in recruitment of proapoptotic WOX1 (also named WWOX or FOR) and formation of Hyal-2.WOX1 complexes for relocation to the nuclei."
Hyaluronidase 2 negatively regulates RON receptor tyrosine kinase and mediates transformation of epithelial cells by jaagsiekte sheep retrovirus.
-
HYAL2 associates with the RON/MST1R receptor tyrosine kinase and holds it functionally silent; releasing RON activates AKT and MAPK signalling.
"the HYAL2 receptor protein is associated with the RON receptor tyrosine kinase (also called MST1R or Stk in the mouse), rendering it functionally silent"
Candidate tumor suppressor HYAL2 is a glycosylphosphatidylinositol (GPI)-anchored cell-surface receptor for jaagsiekte sheep retrovirus, the envelope protein of which mediates oncogenic transformation.
-
HYAL2 is a GPI-anchored cell-surface protein rather than a purely lysosomal enzyme, and its hyaluronidase activity is too weak to detect in cell-based assays that readily detect HYAL1.
"HYAL2 was previously described as a lysosomal hyaluronidase, but we show that HYAL2 is actually a glycosylphosphatidylinositol (GPI)-anchored cell-surface protein."
HYAL2, a human gene expressed in many cells, encodes a lysosomal hyaluronidase with a novel type of specificity.
-
HYAL2 hydrolyses high-molecular-mass hyaluronan only below pH 4 and only down to a ~20 kDa product, defining the acid-dependent, partial-digestion character of the enzyme.
"The HYAL2 protein was shown to have hyaluronidase activity below pH 4."
Skeletal and hematological anomalies in HYAL2-deficient mice: a second type of mucopolysaccharidosis IX?
-
Despite weak in vitro activity, HYAL2 has a physiological hyaluronidase role in vivo, required for craniovertebral bone formation, plasma hyaluronan clearance and erythrocyte and platelet homeostasis.
"murine HYAL2 has a physiological activity in vivo that is relevant for craniovertebral bone formation, maintenance of plasma HA concentrations, and erythrocyte and platelet homeostasis"
UniProt record for naked mole rat Hyal2 (A0A0P6J1Y4)
-
UniProt assigns EC 3.2.1.35, places the protein in glycosyl hydrolase family 56, gives it a cleaved signal peptide and a GPI anchor at the cell membrane, annotates the catalytic proton donor at residue 135, and records an MST1R interaction.
"-!- SIMILARITY: Belongs to the glycosyl hydrolase 56 family."
Affinage mechanistic annotation for HYAL2 (human ortholog), used as a conserved-mechanism baseline
-
A 21-finding, citation-anchored record of the HUMAN HYAL2 protein, used here only to establish what the conserved protein does mechanistically.
"HYAL2 is a GPI-anchored, lipid raft-associated cell-surface hyaluronidase that initiates extracellular catabolism of high-molecular-weight hyaluronan (HA), cleaving it preferentially at acidic pH to ~20 kDa intermediates rather than to smaller fragments"
Automatic transfer of experimentally verified manual GO annotation data to orthologs using Ensembl Compara
Automatic assignment of GO terms using logical inference, based on on inter-ontology links
Combined Automated Annotation using Multiple IEA Methods