Vacuolar protein sorting-associated protein 33A
Function
Plays a role in vesicle-mediated protein trafficking to lysosomal compartments including the endocytic membrane transport and autophagic pathways. Believed to act as a core component of the putative HOPS and CORVET endosomal tethering complexes which are proposed to be involved in the Rab5-to-Rab7 endosome conversion probably implicating MON1A/B, and via binding SNAREs and SNARE complexes to mediate tethering and docking events during SNARE-mediated membrane fusion. The HOPS complex is proposed to be recruited to Rab7 on the late endosomal membrane and to regulate late endocytic, phagocytic and autophagic traffic towards lysosomes. The CORVET complex is proposed to function as a Rab5 effector to mediate early endosome fusion probably in specific endosome subpopulations (PubMed:23351085, PubMed:24554770, PubMed:25266290, PubMed:25783203). Required for fusion of endosomes and autophagosomes with lysosomes; the function is dependent on its association with VPS16 but not VIPAS39 (PubMed:25783203). The function in autophagosome-lysosome fusion implicates STX17 but not UVRAG (PubMed:24554770).
Involvement in disease
Mucopolysaccharidosis-plus syndrome
MPSPS
A form of mucopolysaccharidosis, a group of lysosomal storage diseases characterized by defective degradation of glycosaminoglycans, resulting in their excessive accumulation and secretion. The diseases are progressive and often display a wide spectrum of clinical severity. MPSPS is an autosomal recessive form characterized by coarse facial features, dysostosis multiplex, hepatosplenomegaly, respiratory difficulties, intellectual disability, developmental delay, pyramidal signs, severe chronic anemia, renal involvement and cardiac defects. Laboratory analyses show proteinuria with glomerular foamy cells, excess secretion of urinary glycosaminoglycans, and extremely high levels of plasma heparan sulphate. Disease onset is in infancy. Most patients die in the first years of life due to cardiorespiratory failure.
None
The disease is caused by variants affecting the gene represented in this entry.
Sequence Similarities
Belongs to the STXBP/unc-18/SEC1 family.
Cellular localization
- Cytoplasmic vesicle
- Late endosome membrane
- Peripheral membrane protein
- Cytoplasmic side
- Lysosome membrane
- Peripheral membrane protein
- Cytoplasmic side
- Early endosome
- Cytoplasmic vesicle
- Autophagosome
- Cytoplasmic vesicle
- Clathrin-coated vesicle
Alternative names
Vacuolar protein sorting-associated protein 33A, hVPS33A, VPS33A