Auto catalytic ROS dependent proteolysis of ICA512

TOLEDO P.; LLOVERA R; RASIA R.; ERMÁCORA M

Sierra de la ventana

Congreso; XLIII Reunión Anual de la Sociedad Argentina de Biofísica; 2014

ICA512/IA-2 is a receptor‑type protein-tyrosine phosphatase (RPTP) that localize in secretory granules of various neuroendocrine cells. In pancreatic islet β‑cells, it participates in the regulation of insulin secretion, ensuring proper granulogenesis, and β‑cell proliferation. In previous works we reported the auto catalytic, ROS dependent, proteolysis of the membrane proximal ectodomain of ICA512 (MPE ICA512; residues 448-576). The cleavage observed in vitro removes about 20 amino acids at both the N- and C-termini. To gain further insight in this topic, two shorter version of MPE ICA512, including residues 469 to 576 and 469 to 557, were prepared. The three MPE ICA512 variants were compare with regard to their auto proteolytic properties. It was found that the activity depends of sequential determinants located at residues 557 to 576. The residues in that region presumably bind a redox active metal required for catalysis. The removed tails may be spatially close and for that reason undergo cleavage concomitantly. Since auto proteolytic activity may be an important physiological feature leading to the shedding of the ICA512 ectodomain in vivo, we further investigated the structural properties of the termini. To that end, NMR studies were conducted which showed that the N- and C-terminal region behave in solution as unfolded segments. Those results contribute to our long term effort to prepare a 3D model of the receptor embedded in the membrane.