SNARE proteins: zip codes in vesicle targeting?

Abstract

Membrane traffic in eukaryotic cells is mediated by transport vesicles that bud from a precursor compartment and are transported to their destination compartment where they dock and fuse. To reach their intracellular destination, transport vesicles contain targeting signals such as Rab GTPases and polyphosphoinositides that are recognized by tethering factors in the cytoplasm and that connect the vesicles with their respective destination compartment. The final step, membrane fusion, is mediated by SNARE proteins. SNAREs are connected to targeting signals and tethering factors by multiple interactions. However, it is still debated whether SNAREs only function downstream of targeting and tethering or whether they also participate in regulating targeting specificity. Here, we review the evidence and discuss recent data supporting a role of SNARE proteins as targeting signals in vesicle traffic.

The SNARE protein Vti1b is recruited to the sites of BCR activation but is redundant for antigen internalisation, processing and presentation

“…In our previous proteomic study, we identified the SNARE protein Vti1b among the proteins showing the highest translocation towards the site of BCR activation sites upon antigen encounter ( Awoniyi et al, 2020 ). Although SNARE proteins are critical for membrane fusion events in the cell ( Koike and Jahn, 2022 ), the role of SNAREs, and in particular Vti1b, in B cell biology, remains to be explored. In this work, we found that, despite of enriched localization of Vti1b towards the site of BCR activation and in antigen-containing vesicles, Vti1b-deficient B cells are still able to respond normally to antigen stimulus and process antigen for presentation, suggesting functional redundancy with other SNAREs.…”

The Bcvic1 and Bcvic2 vegetative incompatibility genes in Botrytis cinerea encode proteins with domain architectures involved in allorecognition in other filamentous fungi

“…Specific modifications of a guarded SNARE protein that leads to the NLR initiating a cell death response have not been investigated in any of the fungal VI systems characterised to date. However, since BCVIC2 is putatively designated to act at the plasma membrane, its activation, promoted by Sec1/Munc18 (SM) regulatory proteins or posttranslational modifications, to enable it to participate in forming a SNARE complex [78], or its interaction with tethering factors involved in targeting of membrane fusion events [79], may be sufficient to trigger the guarding NLR.…”

Circulating Exosome Cargoes Contain Functionally Diverse Cancer Biomarkers: From Biogenesis and Function to Purification and Potential Translational Utility

“…For instance, two studies showed that inhibition of lysosome fusion with bafilomycin A1 results in the increased secretion of exosomes [ 214 , 215 ]. The release of exosomes by fusion of the MVB with the plasma membrane involves two sequential steps: (i) The targeted movement of MVBs to the plasma membrane, which is reliant on the structure of the microtubule cytoskeleton and the dynamic mechanisms of molecular motors, including dynein, kinesins, and actin-based myosin [ 216 , 217 ], and is regulated by several small Ras-like GTPases (including Rab27 A/B, Rab11, and Rab35), and soluble NSF attachment protein receptor (SNARE) (i.e., small, abundant tail-anchored proteins which are post-translationally inserted into the plasma membrane) proteins [ 218 , 219 ], which have been shown to differ between different cell types [ 220 , 221 ]. (ii) The fusion with the plasma membrane, wherein Rab11 and Rab35 facilitate MVB and plasma membrane fusion [ 222 , 223 ] through the assembly and functionalization of the “SNAREpin” complex.…”