Changes in mTOR/4‐EBP1 pathway induced by a novel mutation in PRKAG2 gene (864.7)

Abstract

Objective: The genetics of hypertrophic cardiomyopathy (HCM) is heterogeneous. Mutations in PRKAG2 have been implicated in some previous cases of HCM. PRKAG2 encodes the γ2 isoform of AMPK, a heterotrimeric enzyme with major roles in regulation of energy metabolism in response to cellular stress. We have identified a K475E mutation which results in a neonatal HCM phenotype. We have demonstrated that overexpressing the K475E mutant in HEK‐293 cells leads to 1) a markedly increase in the basal phosphorylation of T172 and associated kinase activity; 2) a reduction in the sensitivity to AMP in allosteric activation. The aim of this study was to investigate changes in downstream signaling pathways induced by the mutation.Methods: Primary dermal fibroblast cultures of control and a patient with the K475E mutation were maintained under standard cell culture condition. Cell lysates were subject to Western blotting for downstream factors, including Akt, p70S6K, and 4E‐BP1.Results: K475E mutation results in an increase in the activation of p‐P70S6K as evidenced by increased phosphorylation at both the critical phosphorylation sites (T389 and T421/S424). Fibroblasts from the K475E mutation also show increases in phosphorylation of 4E‐BP1 (S65 and T70).Conclusions: Our study shows K475E mutation leads to activation of a signaling pathway that favors protein synthesis/growth, providing a logical mechanism for the HCM phenotype observed.Grant Funding Source: NIH