Involved in intracellular vesicle trafficking. Identified in a complex containing STX6, STX12, VAMP4 and VTI1A (PubMed:17159904). Binds EEA1 (By similarity). Interacts with VPS45A (By similarity). Interacts with MARCHF2; the interaction promotes MARCHF2-mediated ubiquitination and degradation of CFTR (PubMed:23818989). Interacts with MARCHF3 (By similarity). Interacts with GOPC (PubMed:11384996). Interacts with UHRF1BP1L (via C-terminal coiled-coil domain) (PubMed:20163565). Interacts with BAIAP3; this interaction is increased in the presence of calcium (PubMed:28626000). Belongs to the syntaxin family.