T. Kuroki et al., Cholesterol sulfate, an activator of protein kinase C mediating squamous cell differentiation: a review, MUT RES-R M, 462(2-3), 2000, pp. 189-195
Activity of protein kinase C (PKC) depends on the interaction with polar he
ad-groups of two membrane lipids, i.e., phosphatidylserine and diacylglycer
ol, We demonstrated that cholesterol metabolism is directly involved in act
ivation of the eta isoform of protein kinase C (PKC eta), which is predomin
antly expressed in epithelial tissues in close association with epithelial
differentiation. We found that PKC eta was activated by cholesterol sulfate
(CS), a metabolite of cholesterol formed during squamous cell differentiat
ion. in the presence of CS, phorbol ester only weakly enhanced the activity
of PKC eta. CS also activated PKC eta, PKC delta and PKC epsilon in a dose
-dependent manner, when assayed using purified recombinant materials. Howev
er, when partially purified materials were used from overexpressing normal
human keratinocytes, only PKC eta was activated by CS among the isoforms ex
amined. All the existing lines of evidence, mainly supplied from our labora
tory, suggest that CS is involved in a signal transduction of squamous cell
differentiation and thereby modifying squamous cell carcinogenesis. (C) 20
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