Contribution of P62 to the Phenotype Transition of Coronary Arterial Myocytes from Mice Lacking CD38 Gene

Abstract

Recent studies have shown that CD38 gene deletion and associated lysosomal dysfunction impaired autophagic flux and thereby resulted in enhanced synthetic phenotype in mouse coronary arterial myocytes (CAMs). However, the mechanism is still unclear. Given the accumulation of p62 during autophagic flux failure and its main role in the regulation of cell proliferation and differentiation, we hypothesized that p62 mediates CD38 deficiency induced phenotype transition in CAMs. By Western blot and confocal microscopic analysis, we found that CAMs from CD38-/- mice markedly overexpressed vimentin as indicative marker for dedifferentiation, which was mimicked and enhanced by bafilomycin A1 (Baf). Baf and CD38 gene deletion significantly increased the proliferation rate of CAMs and reduced G2/M phase cell populations, namely, reduction of the G2-M arrest to allow cells to enter mitosis. All of these effects were significantly suppressed by p62 gene silencing. In addition, cyclin-dependent kinase 1 (Cdk1) was found significantly increased in CAMs with Baf treatment or CD38 gene deletion, which was markedly attenuated by p62 siRNA. In animal experiments, coronary arterial wall from CD38-/- mice or mice receiving chloroquine (4 mg/kg/d, ip), a lysosome inhibitor had large increase in p62, vimentin and CDK1. These results indicate that p62 accumulation due to lysosome dysfunction enhances a phenotype transition of CAMs to a dedifferentiation status, which is associated with inhibition of G2/M arrest and enhanced CDK1 expression. This phenotype change may promote CAMs to become more proliferative leading to atherogenesis (Supported by NIH grants HL057244, HL075316, HL091464 and HL122937).