Function of Syntaxin11 in cytotoxic T lymphocytes (121.9)

Abstract

Abstract Cytotoxic T Lymphocytes (CTLs) form immunological synapses (IS) with antigen presenting cells to kill them. Killing requires the fusion of lytic granules at the IS to release the containing cytotoxic molecules (perforin and granzymes). The fusion process is mediated by SNARE (soluble N-ethylmaleimide sensitive factor attachment protein receptor) proteins. Since mutations within the coding region of syntaxin11 lead to Familial Hemophagocytic Lymphohistiocytosis (FHL4), an immune disorder caused by impaired granule exocytosis. We have investigated the contribution of syntaxin11 to lytic granule release. Using CD3 specific antibodies as a marker for a functional IS, we show that syntaxin11 accumulates at the IS in CTLs. Syntaxin11 was also co-localized with Munc18-2, a docking factor in agreement with the role of Munc18-2 as a syntaxin chaperone in other cell types. Using high resolution nanoscopy (structured illumination microscopy) we determined the subcellular localization of syntaxin11 in CTLs with a syntaxin11 specific antibody. Syntaxin11 was associated with recycling endosomes and mannose 6-phosphate receptor (M6PR) positive compartments. Functional assays using Syntaxin11 specific siRNA (knockdown studies) show a reduction in degranulation and killing efficiency in contrast to control siRNA transfected CTLs. These results support the conclusion that syntaxin11 is required for lytic granule exocytosis.