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PDZ domains are one of the most common protein-protein interaction domains in human. PDZ domain containing 2 protein (PDZD2) contains 6 PDZ domains and is highly expressed in pancreatic beta cells. It undergoes cleavage in the endoplasmic reticulum to produce a secreted form PDZD2 (sPDZD2) which retains the last two PDZ domains of PDZD2. sPDZD2 is a candidate beta cell regulatory factor. In current study, two mutated forms of sPDZD2 were generated with alterations in the amino acid sequence within the carboxylate-binding loop of one of the two PDZ domains, either at the PDZ5 or at the PDZ6 domain. Current study revealed that both the PDZ5-mutated and PDZ6-mutated sPDZD2 proteins failed to exert the insulinotropic effect that the wildtype sPDZD2 had on INS-1E cells when added exogenously in the culture medium. Both mutant proteins also failed to rescue the silencing action of siRNA on the insulinotropic effect of endogenous PDZD2 in INS-1E cells. These results suggest that intact carboxylate-binding loops of both PDZ5 and PDZ6 domain are crucial for the insulinotropic effect of sPDZD2 exerting on INS-1E cells.
About the author
Dr Winnie Wat was graduated at the medical school of the University of Hong Kong in 1997. She works as an endocrinologist in Hong Kong. In 2009, She pursued her degree in Master of Medical Sciences at her alma mater and engaged in research on the insulinotropic effect of secreted PDZD2.
