STX5

STX5, also known as syntaxin-5, is a human gene that encodes a member of the syntaxin family of SNARE (soluble NSF attachment protein receptor) proteins. STX5 functions as a target membrane SNARE involved in vesicle fusion within the early secretory pathway, with key roles in trafficking between the endoplasmic reticulum and the Golgi apparatus and in intra-Golgi transport. By assembling with partner SNAREs on opposing membranes, STX5 supports the selective fusion of transport vesicles carrying secretory and membrane proteins.

The STX5 gene gives rise to multiple protein isoforms, typically including at least two major forms that differ in their N-terminal regions. These isoforms localize to the ER-Golgi network and can have distinct subcellular distributions, contributing to specialization within vesicular trafficking routes. The protein is primarily associated with membranes of the ER and Golgi, reflecting its central role in coordinating cargo movement through the early secretory pathway.

In terms of structure, syntaxin-5 exhibits the characteristic SNARE motif necessary for complex formation and a C-terminal transmembrane domain that anchors the protein to membranes. As with other SNAREs, STX5 activity is regulated by interactions with SM (Sec1/Munc18-like) proteins, which modulate SNARE complex assembly and membrane fusion efficiency.

Clinical relevance of STX5 is mainly explored in the context of cellular trafficking and Golgi biology. Alterations in STX5 expression or function can disrupt proper protein sorting and glycoprotein processing, illustrating its importance for cellular homeostasis. STX5 remains a common subject of study in cell biology and neurobiology related to vesicular transport.