ST5

This gene was identified by its ability to suppress the tumorigenicity of Hela cells in nude mice. The protein encoded by this gene contains a C-terminal region that shares similarity with the Rab 3 family of small GTP binding proteins. This protein preferentially binds to the SH3 domain of c-Abl kinase, and acts as a regulator of MAPK1/ERK2 kinase, which may contribute to its ability to reduce the tumorigenic phenotype in cells. Three alternatively spliced transcript variants of this gene encoding distinct isoforms are identified. [provided by RefSeq]

suppression of tumorigenicity 5

Isoform 1
May be involved in cytoskeletal organization and tumorogenicity. Seems to be involved in a signaling transduction pathway leading to activation of MAPK1/ERK2. Plays a role in EGFR trafficking from recycling endosomes back to the cell membrane (PubMed:29030480).
Isoform 2
Guanine nucleotide exchange factor (GEF) which may activate RAB9A and RAB9B. Promotes the exchange of GDP to GTP, converting inactive GDP-bound Rab proteins into their active GTP-bound form.
Isoform 3
May block ERK2 activation stimulated by ABL1 (Probable). May alter cell morphology and cell growth (Probable).

Positive regulation of ERK1 and ERK2 cascade

Isoform 1
Cytoplasm, cell cortex
Cell membrane
Recycling endosome
Colocalizes with RAB13 and ITSN1 at cytoplasmic vesicles that are most likely recycling endosomes. Colocalizes with the cortical actin cytoskeleton.

Phosphorylated. Phosphorylation decreases ITSN1 binding.