Complexin 2 is necessary for efficient GLUT4 exocytosis in L6 cells.

KLIP, AMIRA; MAYORGA LS; PAVAROTTI MARTÍN A

Buenos Aires

Congreso; Reunión conjunta de sociedades de biociencias; 2017

Reunión Conjunta de Sociedades de BioCiencias

The glucose transporter type 4 (GLUT4) is the insulin-regulated glucose transport expressed mainly in striated muscle and adipose tissues. It is well known that insulin mediates the glucose uptake by GLUT4 traffic from intracellular storage (GSVs/IRVs) to the PM, a process also known as ?GLUT4 translocation? or ?GLUT4 exocytosis?. Similarly, muscle contraction also increases the GLUT4-exocytosis. Glucose transport is a rate limiting process for glucose utilization in adipose and muscle tissues, and it is deficient in type 2 diabetes. Intracellular membrane fusions are carried out by canonical SNAREs proteins, which are constitutively active and require a large set of regulatory proteins. In this regard, the calcium sensor synaptotagmin and complexin play a key role in calcium regulated exocytosis in neuroendocrine cells and spermatozoa. Specifically, the t-SNAREs, sintaxin-4 and SNAP23, and the v-SNARE Vamp2 are the main SNAREs in GLUT4-exocytosis. It is well established that this process requires calcium and calcium sensors (ESYT1 and Doc2B), however, there are non-evidences about the presences and participation of complexin during this process in muscle cells. Therefore, the purpose of this work was to study the presences of complexin in muscle cells and its participation in GLUT4 exocytosis. Using approaches like western-blot, immunofluorescence and qPCR we were able to show the presence of complexin in L6-muscle cells and skeletal muscle tissue, being complexin II the most abundant isoform. Moreover, using specific complexins siRNA, we knocked-down the protein expression in L6 cells expressing GLUT4 with a myc tag. Using these cells, we setted up a GLUT4 translocation assay and we observed a deficient GLUT4-exocytosis in complexin-KD cells, compared with control cells. Therefore, this is the first study which evidence of complexin II expression in tissue and cells muscle, showing, furthermore, that complexin II is required for GLUT4 exocytosis in L6 cells.