“Differential spatio-temporal dynamics of endocytosis and signaling of insulin receptor A and B

GIUDICE JIMENA; COLUCCIO LESKOW FEDERICO; ARNDT-JOVIN DONNA; JOVIN THOMAS M; JARES-ERIJMAN ELIZABETH

Los Cocos. Córdoba- Argentina

Congreso; THE FIRST SOUTH AMERICAN SPRING SYMPOSIUM IN SIGNAL TRANSDUCTION AND MOLECULAR MEDICINE; 2010

Insulin signaling is involved in glucose metabolism and cellular growth. Impaired response to insulin is the hallmark of diabetes while upregulated insulin activity occurs in many cancer types. Two splice variants of the insulin receptor (IR) exist in mammals: IR-A lacking exon 11, involved in mitogenic signaling, and the full length IR-B responsible for the metabolic response. Although considerable biochemical data exist on insulin binding and signaling, little is known about the differential spatio temporal dynamics of IR isoforms and its possible effects on signaling. To gain insight into the dynamics of the activation and internalization of IR isoforms by microscopy we combined 2 techniques: streptavidin-quantum dots conjugated with biotinylated ligands; and visible fluorescent proteins. Using confocal and programmable array microscopy (PAM), we visualized endocytosis of both isoforms in living and fixed cells and in a cell-by-cell study we demonstrated a higher rate of endocytosis of IR-A compared to IR-B. These differences correlated with higher and sustained activation of IR-A in response to insulin and distinctive ERK 1/2 activation profiles and gene transcription regulation, suggesting a mechanism for the differential signaling in response to insulin.