ALTERED CHOLESTEROL TRAFFICKING IN HERPESVIRUS-INFECTED ARTERIAL CELLS - EVIDENCE FOR VIRAL PROTEIN KINASE-MEDIATED CHOLESTEROL ACCUMULATION

Herpesvirus infection of arterial smooth muscle cells has been shown t o cause cholesteryl ester (CE) accumulation. However, the effects of h uman herpes simplex virus type 1 (HSV-1) infection on cholesterol bind ing and internalization, intracellular metabolism, and efflux have not been evaluated. In addition, the effects of viral infection on signal transduction pathways that impact upon cholesterol metabolism have no t been studied. We show in studies reported herein that HSV-1 infectio n of arterial smooth muscle cells enhances low density lipoprotein (LD L) binding and uptake which parallels an increase in LDL receptor stea dy state mRNA levels and transcription of the LDL receptor gene. HSV-1 also increases CE synthesis and 5-hydroxy-3-methylglutaryl-CoA reduct ase activity but concomitantly reduces CE hydrolysis and cholesterol e fflux. Interestingly, this viral infection was associated with a time- dependent decrease in protein kinase A activity and an increase in vir al-induced protein kinase (VPK) activity commensurate with the accumul ation of esterified cholesterol. The relationship between increased VP K activity and alterations in CE accumulation in virally infected cell s was explored using an HSV-1 VPK- mutant in which the portion of the HSV-1 genome encoding VPK had been deleted. Cholesteryl ester accumula tion was significantly increased (>50-fold) in HSV-1-infected cells co mpared to uninfected cells. However, the HSV-1 VPK- mutant had no sign ificant effect on CE accumulation. The relationship between VPK activi ty and these alterations in cholesterol metabolism was further support ed by the observation that staurosporine and calphostin C (protein kin ase inhibitors) reduced protein kinase activity in HSV-l-infected cell s. These results suggest several potential mechanisms by which alterat ions in kinase activities in response to HSV-1 infection of vascular c ells may alter cholesterol trafficking processes that eventually lead to CE accumulation.