Syntaxin 1C, a soluble form of syntaxin, attenuates membrane recycling by destabilizing microtubules

Abstract

SummarySyntaxin 1C (STX1C), produced by alternative splicing of the stx1A gene, is a soluble syntaxin lacking a SNARE domain and a transmembrane domain. It is unclear how soluble syntaxin can control intracellular membrane trafficking. We found that STX1C affected microtubule (MT) dynamics through its tubulin-binding domain (TBD) and regulated recycling of intracellular vesicles carrying glucose transporter-1 (GLUT1). We demonstrated that the amino acid sequence VRSK of the TBD was important for the interaction between STX1C and tubulin and that wild-type STX1C (STX1C-WT), but not the TBD mutant, reduced the V max of glucose transport and GLUT1 translocation to the plasma membrane in FRSK cells. Moreover, by time-lapse analysis, we revealed that STX1C-WT suppressed MT stability and vesicle-transport motility in cells expressing GFP-a-tubulin, whereas TBD mutants had no effect. We also identified that GLUT1 was recycled in the 45 minutes after endocytosis and that GLUT1 vesicles moved along with MTs. Finally, we showed, by a recycling assay and FCM analysis, that STX1C-WT delayed the recycling phase of GLUT1 to PM, without affecting the endocytotic process of GLUT1. These data indicate that STX1C delays the GLUT1 recycling phase by suppressing MT stability and vesicle-transport motility through its TBD, providing the first insight into how soluble syntaxin controls membrane trafficking.

Increased glucose metabolic activity is associated with CD4+ T-cell activation and depletion during chronic HIV infection

“…Interestingly, the R&D Glut1 antibody detected intra-cellular but not cell surface Glut1 in NIH3T3 cells that were overexpressing Glut1, an observation that is not consistent with the suggestion that the antibody interacts with a different cell surface protein that is associated with Glut-1 overexpression in transformed cells [32]. More recently, this antibody has been shown by others to be specific for Glut1 [40] and has been used to evaluate Glut1 expression on cell surfaces [28,29] including T cells in a cohort of HIV-infected individuals [30]. We have also clearly shown increased intracellular Glut1 (using a Glut-1 cterm antibody), increased Glut1 mRNA, and increased glucose uptake in CD4 + T cells in HIV+/naive individuals, all of which is consistent with increased glucose metabolic activity.…”

Structure of, and functional insight into the GLUT family of membrane transporters

“…For example, GLUT1 carrying intracellular vesicles are upregulated by protein kinase C and casein kinase substrate 3 (PACSIN 3) in adipocytes and downregulated by Syntaxin 1C (STX1C) in a lung epithelial cell line. 132,133 STX1C is a soluble syntaxin suppressing the stability of microtubules and vesicle transport mobility, whereas PACSIN 3 is an adaptor protein involved in regulation of cellular cytoskeletal elements and the clathrin-coated pit pathway. Trafficking of GLUT1 from an intracellular pool to the plasma membrane is also increased by AMP kinase in murine brain microvasculature endothelium bEnd.3 cells.…”

NFAT1 and NFAT3 Cooperate with HDAC4 during Regulation of Alternative Splicing of PMCA Isoforms in PC12 Cells

“…Cells were lysed in RIPA buffer and samples for immunoprecipitation were obtained with agarose beads with protein A/G (Santa Cruz, USA) as described [19]. Samples were incubated for 2 h at 4°C with mouse monoclonal anti-NFAT1 antibody (Abcam, USA) or with rabbit polyclonal anti-NFAT3 antibody (Cell Signaling, USA).…”