Protein-kinase-C? expression correlates with enhanced keratinocyte proliferation in normal and neoplastic mouse epidermis and in cell culture

Abstract

In order to gain insight into the biological function of a PKC iso‐enzyme, the protein kinase Cμ, we analyzed the expression pattern of this protein in mouse epidermis and keratinocytes in culture. Daily analysis of neonatal mouse epidermis immediately after birth showed a time‐dependent reduction in the PKCμ content. Expression of the proliferating‐cell nuclear antigen (PCNA), indicative of the proliferative state of cells, was reduced synchronously with PKCμ as the hyperplastic state of the neonatal tissue declined. In epidermal mouse keratinocytes, fractionated according to their maturation state, PKCμ expression was restricted to PCNA‐positive basal‐cell fractions. In primary cultures of those cells, growth arrest and induction of terminal differentiation by Ca2+ resulted in strongly reduced PKCμ expression, concomitantly with the loss of PCNA expression. Treatment of PMK‐R1 keratinocytes with 100 nM of the mitogen 12‐O‐tetradecanoylphorbol‐13‐acetate (TPA) resulted in activation of PKCμ, reflected by translocation from the cytosolic to the particulate fraction and by shifts in electrophoretic mobility. DNA synthesis was significantly inhibited by the PKCμ inhibitor Goedecke 6976, while Goedecke 6983 did not inhibit PKCμ. Carcinomas generated according to the 2‐stage carcinogenesis protocol in mouse skin consistently exhibited high levels of PKCμ. These data correlate PKCμ expression with the proliferative state of murine keratinocytes and point to a role of PKCμ in growth stimulation. A correlation between PKCμ expression and enhanced cell proliferation was also observed for NIH3T3 fibroblasts transfected with and over‐expressing human PKCμ. Int. J. Cancer 80:98–103, 1999. © 1999 Wiley‐Liss, Inc.

IL-4 and IL-13, But Not IL-10, Protect Human Synoviocytes from Apoptosis

“…The differential results obtained in this study with Gö6983, Gö6976, and bisindolylmaleimide I suggest that activation of PKC may be responsible for cell protection by IL-4. Recently, PKC expression was also found to be correlated with the proliferative state of murine keratinocytes and NIH3T3 fibroblasts (31). These results are also consistent with a recent study showing that inhibition of PKC with Gö6976 results in a significant increase of both caspase 3 and caspase 8 activity in anti-Fas-treated Jurkat cells (32).…”

Putative Conventional Protein Kinase C Inhibitor Gödecke 6976 [12-(2-Cyanoethyl)-6,7,12,13-tetrahydro-13-methyl-5-oxo-5H-indolo(2,3-a)pyrrolo(3,4-c)-carbazole] Stimulates Transglutaminase Activity in Primary Mouse Epidermal Keratinocytes

“…Like calcium/calmodulin-dependent protein kinase II (Soderling, 1996), PKD also demonstrates an autophosphorylationmediated constitutive activity following its activation (Waldron et al, 1999). PKD activity increases with the addition of factors such as bombesin, vasopressin, and platelet-derived growth factor in Swiss 3T3 cells (Zugaza et al, 1997), and it has been shown that there is an increase in mitogenesis with PKD overexpression in fibroblasts (Rennecke et al, 1999;Zhukova et al, 2001). In addition, PKD levels are increased in cutaneous carcinomas and the proliferating compartment of mouse skin (Rennecke et al, 1999).…”

“…PKD activity increases with the addition of factors such as bombesin, vasopressin, and platelet-derived growth factor in Swiss 3T3 cells (Zugaza et al, 1997), and it has been shown that there is an increase in mitogenesis with PKD overexpression in fibroblasts (Rennecke et al, 1999;Zhukova et al, 2001). In addition, PKD levels are increased in cutaneous carcinomas and the proliferating compartment of mouse skin (Rennecke et al, 1999). Thus, we hypothesized that PKD might play an antidifferentiative or proproliferative role in keratinocytes.…”

Phospholipase D Signaling and Extracellular Signal-Regulated Kinase-1 and -2 Phosphorylation (Activation) Are Required for Maximal Phorbol Ester-Induced Transglutaminase Activity, a Marker of Keratinocyte Differentiation

“…Indeed, we have previously shown that Gö 6976, but not the other PKC inhibitors mentioned above, stimulates transglutaminase activity and enhances the effect of 1,25-dihydroxyvitamin D 3 in keratinocytes (Shapiro et al, 2002). Similarly, we (Shapiro et al, 2002) and others (Rennecke et al, 1999) have shown that Gö 6976, but not Gö 6983, inhibits DNA synthesis in keratinocytes as well. Furthermore, we have proposed that PKD serves as a proproliferative and/or antidifferentiative signaling enzyme in these cells (Shapiro et al, 2002; M. E. Dodd, V. L. Ristich, S. Ray, R. M. Lober, and W. B. Bollag, manuscript submitted for publication; for review, see Bollag et al, 2004).…”