Sorting nexin-5 (SNX5) belongs to the sorting nexin family, which contains a conserved PX (phox homology) domain that is responsible for binding to specific phosphoinositides []. SNX5 also contains a BAR domain that is C terminus to the PX domain. Besides being involved in several stages of intracellular trafficking, SNX5 also plays a role in macropinocytosis and in the internalisation of EGFR after EGF stimulation [, ].
This entry represents the PX domain found in Sorting nexin-5 (SNX5). The PX domain of SNX5 binds phosphatidylinositol-3-phosphate (PI3P) and PI(3,4)P2. SNX5 is localized to a subdomain of early endosome and is recruited to the plasma membrane following EGF stimulation and elevation of PI(3,4)P2 levels [].The Phox Homology (PX) domain is a phosphoinositide (PI) binding module present in many proteins with diverse functions. Sorting nexins (SNXs) make up the largest group among PX domain containing proteins. They are involved in regulating membrane traffic and protein sorting in the endosomal system. The PX domain of SNXs binds phosphoinositides (PIs) and targets the protein to PI-enriched membranes [, ]. SNXs differ from each other in PI-binding specificity and affinity, and the presence of other protein-protein interaction domains, which help determine subcellular localization and specific function in the endocytic pathway [, , ].
Sorting nexins (SNXs) are a diverse group of cellular trafficking proteins that are unified by the presence of a phospholipid-binding motif, the PX domain. The ability of these proteins to bind specific phospholipids, as well as their propensity to form protein-protein complexes, points to a role for these proteins in membrane trafficking and protein sorting []. Members of this group also contain coiled-coil regions within their large C-terminal domains and a BAR domain, whose function has been defined as a dimerisation motif, as sensing and inducing membrane curvature, and/or likely to bind to small GTPases [].This entry includes SNX5, SNX6 and SNX32 (also known as SNX6B).SNX5 contains a BAR domain that is C teminus to the PX domain. SNX5 plays a role in macropinocytosis []and in the internalisation of EGFR after EGF stimulation [].SNX6 was found to interact with members of the transforming growth factor-beta family of receptor serine/threonine kinases. Strong heteromeric interactions were also seen among SNX1, -2, -4, and -6, suggesting the formation in vivoof oligomeric complexes. SNX6 is localized in the cytoplasm where it is thought to target proteins to the trans-Golgi network []. In addition, SNX6 was found to be translocated from the cytoplasm to nucleus by Pim-1, an oncogene product of serine/threonine kinase. This translocation is not affected by Pim-1-dependent phosphorylation, but the functional significance is unknown [].
