About VPS / Vacuolar Protein Sorting:
The phosphatidylinositols family has a significant role to play in the identification of membrane and intracellular trafficking processes. Vacuolar proteins are found to reach different vacuoles through vesicle-mediated biosynthetic trafficking pathways.
In plant cells, there are two types of membrane receptors; the receptor membrane ring-H2 family and the vacuolar sorting receptor family.
In yeast and animals, PtdIn-3-phosphate needed for endosomal sorting, autophagy, and vacuolar trafficking is found conserved kinase complexes made up of autophagy-related AND vacuolar protein sorting (VPS).
Protein sorting genes, Vps23p and Vps27p, function in sequence in the vacuolar sorting mechanism. They also bind directly to the ubiquitinated membrane cargo through the ubiquitin-interacting domain.
Vps23p and Vps27p are mainly assembled into massive multiprotein complexes sequentially recruited to the endosome membrane. This helps to enhance vacuolar sorting. Mammalian vacuolar protein sorting proteins are established and required for sorting EGP receptors.
Vacuolar Protein Sorting Mechanism
Various signaling receptors need ubiquitin covalent modification for agonist-induced down-regulation through endocytic transport to lysosomes. The conserved set of endosome-associating proteins enhances this process. The endosome-associating proteins are also required for vacuolar protein sorting in yeast.
VPS proteins are also crucial in the intracellular sorting and transportation of soluble vacuolar proteins. Additionally, VPS proteins are part of the endosomal sorting complex required for transport, which performs bending and scission reaction of the topologically unique membrane from the cytoplasm.
The endosomal sorting complex required for the transport process is vital in cytokinesis, multivesicular body pathways, and HIV budding.
There are five types of endosomal sorting complex required for transport complexes, and each has a distinct role. Accordingly, the retromer comprises two functional subunits known as the sorting nexin subunit and the cargo-selective subunit.