Sustained phospholipase D activation is associated with keratinocyte differentiation

• Published in: Carcinogenesis (New York) Vol. 20; no. 4; pp. 569 - 576
• Main Authors: Jung, EunMi, Betancourt-Calle, Soraya, Mann-Blakeney, RaShawn, Griner, Richard D., Bollag, Wendy Bollinger
• Format: Journal Article
• Language: English
• Published: Oxford Oxford University Press 01.04.1999; Oxford Publishing Limited (England)
• Subjects: 12-O-tetradecanoylphorbol-13-acetate; 2-diacylglycerol; Animals; Biological and medical sciences; bovine serum albumin; Bradykinin - pharmacology; BSA; Cell Differentiation - drug effects; Cell differentiation, maturation, development, hematopoiesis; Cell physiology; DAG; Enzyme Activation - drug effects; FBS; fetal bovine serum; Fundamental and applied biological sciences. Psychology; half-maximal inhibitory concentration; IC50; insulin transferrin and selenious acid; ITS; ITS + linoleic acid/BSA; Keratinocytes - cytology; Keratinocytes - drug effects; Keratinocytes - enzymology; MEM; Mice; minimum essential medium; Molecular and cellular biology; PEt; phosphatidic acid; Phosphatidic Acids - biosynthesis; phosphatidylethanol; Phosphatidylethanolamines - biosynthesis; phospholipase D; Phospholipase D - physiology; PKC; PLD; Protein Isoforms - agonists; Protein Isoforms - physiology; protein kinase C; Protein Kinase C - drug effects; Protein Kinase C - physiology; SDS; serum-free keratinocyte medium; SFKM; sn-1; sodium dodecyl sulfate; staurosporine; Staurosporine - pharmacology; Stsp; TCA; Tetradecanoylphorbol Acetate - pharmacology; TPA; Transglutaminases - metabolism; trichloroacetic acid; Protein kinase C; Enzyme; Transferases; Rodentia; Biological marker; Esterases; Phosphoric diester hydrolases; Cell differentiation; In vitro; Phospholipase D; Signal transduction; Vertebrata; Mammalia; Enzymatic activity; Mouse; Animal; Bradykinin; Hydrolases; Keratinocyte; Mechanism of action
• DOI: 10.1093/carcin/20.4.569
• ISSN: 0143-3334

Our previous results and data in the literature have suggested a potential role for phospholipase D (PLD) in the regulation of epidermal keratinocyte growth and differentiation. Therefore, we investigated the effect of agents reported to modulate keratinocyte growth and differentiation on PLD activation. The purported protein kinase C (PKC) `inhibitor', staurosporine (Stsp), has been reported to activate PKC in keratinocytes, eliciting many of the same effects as active tumor promoters such as 12-O-tetradecanoylphorbol-13-acetate (TPA). Stsp also induces a programmed pattern of differentiation similar to that seen in keratinocytes in vivo; TPA, on the other hand, appears to preferentially elicit markers consistent with late (granular) differentiation. In contrast, bradykinin is reported to stimulate keratinocyte proliferation. We found that these three agents had different effects on PLD activation in primary mouse epidermal keratinocytes. TPA increased PLD activity acutely and in a sustained fashion. In contrast, Stsp did not acutely activate PLD and inhibited acute TPA-induced activation of PLD. However, treatment of keratinocytes with Stsp for longer time periods (3–5 h) induced sustained PLD activation and this long-term effect was additive with that of TPA. Bradykinin activated PLD acutely but transiently. Both TPA and Stsp increased transglutaminase activity, a marker of late differentiation, whereas bradykinin had little or no effect on either cell proliferation or transglutaminase activity. These results suggest that a sustained activation of PLD is associated with the induction of keratinocyte differentiation. We hypothesize that PLD activity mediates late keratinocyte differentiation through generation of diacylglycerol and activation of specific PKC isoforms. Furthermore, we propose that the profound and immediate TPA-induced stimulation of PLD activity `drives' the keratinocytes to late differentiation steps. However, the less efficacious (and more gradual) sustained activation of PLD by Stsp may allow a patterned differentiation more like that observed in skin.