STX19 is an unusual Qa-SNARE as it lacks a C-terminal transmembrane domain. However, it is efficiently targeted to post-Golgi membranes. We have set out to determine the intracellular localisation of endogenous STX19 and elucidate the mechanism by which it is targeted to membranes. We have found that a pool of STX19 is localised to tubular recycling endosomes where it co-localises with MICAL-L1 and Rab8. Using a combination of genetic, biochemical and cell based approaches we have identified that STX19 is S-acylated at its C-terminus and is a substrate for several Golgi localised S-acyltransferases, suggesting that STX19 is initially S-acylated at the Golgi before trafficking to the plasma membrane and endosomes. Surprisingly, we have found that S-acylation is the key determinant in targeting STX19 to tubular recycling endosomes, suggesting that S-acylation may play a general role in directing proteins to this compartment. In addition, S-acylation also protects STX19 from proteosomal degradation indicating that S-acylation regulates the function of STX19 at multiple levels.
Ampah, K. K., Greaves, J., Shun-Shion, A. S. M., Asnawi, A. W. B. A., Lidster, J. A., Chamberlain, L. H., Collins, M. O., & Peden, A. A. (2018). S-acylation regulates the trafficking and stability of the unconventional Q-SNARE STX19. Journal of Cell Science. https://doi.org/10.1242/jcs.212498