Effects of mevalonate kinase interference on cell differentiation, apoptosis, prenylation and geranylgeranylation of human keratinocytes are attenuated by farnesyl pyrophosphate or geranylgeranyl pyrophosphate

Abstract

Mevalonate kinase (MVK) mutations were previously identified in disseminated superficial actinic porokeratosis. However, the role of MVK in differentiation, apoptosis and prenylation of keratinocytes requires further investigation. Farnesyl pyrophosphate (FPP) and geranylgeranyl pyrophosphate (GGPP) of the mevalonate pathway attach to small G proteins, and serve as molecular switches in biochemical pathways. Therefore, the aim of the present study was to investigate the role of MVK in the expression of keratin 1 and involucrin, apoptosis, protein prenylation and the processing of small G proteins. HaCat human keratinocytes were transfected with viruses carrying MVK interference and overexpression vectors, respectively. The mRNA expression of MVK, keratin 1 and involucrin was detected by reverse transcription-quantitative PCR. Protein expression of MVK, keratin 1, involucrin, lamin A, HRAS, KRAS, NRAS, Rho E, Rho B, Rho A, RAC1 and cdc42 in HaCat cells was detected by western blotting. The apoptotic rates of HaCat cells and protein prenylation levels were examined by flow cytometry. The expression of MVK in HaCat cells was significantly decreased in the interference groups, and markedly increased in the overexpression group compared with the negative control groups. The mRNA and protein expression levels of keratin 1 and involucrin were significantly decreased following interference of MVK expression, and the decrease was markedly attenuated by FPP. Furthermore, the apoptotic rate was markedly increased following MVK interference, and the increase was significantly attenuated by GGPP. The overexpression of MVK significantly decreased the apoptotic rate of HaCat cells. The prenylation levels after MVK interference was notably decreased, which was markedly attenuated by GGPP. The overexpression of MVK significantly increased the prenylation levels of HaCat cells. FPP or GGPP reversed MVK interference-induced decrease in geranylgeranylation levels of lamin A, HRAS, KRAS, NRAS, Rho E, Rho B, Rho A, RAC1 and cdc42. In conclusion, MVK interference decreases the expression of differentiation markers, increases apoptosis, and decreases protein prenylation and geranylgeranylation levels in keratinocytes. These changes are attenuated by FPP or GGPP.