A126 in the active site and TI167/168 in the TI loop are essential determinants of the substrate specificity of PTEN.

A126 in the active site and TI167/168 in the TI loop are essential determinants of the substrate specificity of PTEN.
Cell Mol Life Sci. 2018 Jul 09;:
Authors: Leitner MG, Hobiger K, Mavrantoni A, Feuer A, Oberwinkler J, Oliver D, Halaszovich CR
Abstract
PTEN prevents tumor genesis by antagonizing the PI3 kinase/Akt pathway through D3 site phosphatase activity toward PI(3,4)P2 and PI(3,4,5)P3. The structural determinants of this important specificity remain unknown. Interestingly, PTEN shares remarkable homology to voltage-sensitive phosphatases (VSPs) that dephosphorylate D5 and D3 sites of PI(4,5)P2, PI(3,4)P2, and PI(3,4,5)P3. Since the catalytic center of PTEN and VSPs differ markedly only in TI/gating loop and active site motif, we wondered whether these differences explained the variation of their substrate specificity. Therefore, we introduced mutations into PTEN to mimic corresponding sequences of VSPs and studied phosphatase activity in living cells utilizing engineered, voltage switchable PTENCiV, a Ci-VSP/PTEN chimera that retains D3 site activity of the native enzyme. Substrate specificity of this enzyme was analyzed with whole-cell patch clamp in combination with total internal reflection fluorescence microscopy and genetically encoded phosphoinositide sensors. In PTENCiV, mutating TI167/168 in the TI loop into the corresponding ET pair of VSPs induced VSP-like D5 phosphatase activity toward PI(3,4,5)P3, but not toward P...

Source: Cellular and Molecular Life Sciences : CMLS - July 9, 2018 Category: Cytology Authors: Leitner MG, Hobiger K, Mavrantoni A, Feuer A, Oberwinkler J, Oliver D, Halaszovich CR Tags: Cell Mol Life Sci Source Type: research