Synaptotagmin-like protein 4 (IPR028694)

Short name: SYTL4

Overlapping homologous superfamilies


Family relationships



Synaptotagmin-like protein 4 (SYTL4, Slp4), also known as granuphilin or exophilin-2, belongs to the synaptotagmin-like protein family, which contains a N-terminal RabBD (Rab-binding) domain and two C-terminal C2 domains [PMID: 14745138]. The characteristic feature of the Slp family is the N-terminal domain (referred to as SHD for Slp Homology Domain), which is not found in other C-type tandem C2 proteins [PMID: 12051743].

There are several alternatively spliced isoform of Slp4. Slp4-a (granuphilin-a) has two C2 domains, whereas Slp4-b (granuphilin-b) contains only the first C2 domain. Expression of Slp4-a inhibits regulated secretion in endocrine cells. Slp4-a binds to both the GTP- and GDP-bound forms of Rab27A and inhibits a specific GTP/GDP exchange cycle required for dense-core vesicle exocytosis [PMID: 12590134]. Slp4 has been detected in the pancreatic islet, in particular in insulin-positive beta cells, and in pituitary [PMID: 10497219].

GO terms

Biological Process

GO:0006887 exocytosis

Molecular Function

GO:0017137 Rab GTPase binding

Cellular Component

No terms assigned in this category.

Contributing signatures

Signatures from InterPro member databases are used to construct an entry.