PHORBOL-MYRISTATE-ACETATE, BUT NOT INTERLEUKIN-1-BETA OR INSULIN-LIKEGROWTH-FACTOR-I, REGULATES PROTEIN-KINASE-C ISOENZYMES IN HUMAN DERMAL PAPILLA CELLS

The in vitro growth of human hair follicles is inhibited by interleuki n (IL)-1 beta and phorbol esters, such as phorbol-myristate-acetate (P MA), but enhanced by insulin-like growth factor (IGF)-I. Although this process is only incompletely understood, the dermal papilla as a pivo tal part of the hair follicle is almost certainly involved. Since prot ein kinase C (PKC) isoenzymes are activated by phorbol esters and are key enzymes in signalling pathways of several hormones, neurotransmitt ers, and growth factors, we addressed the question whether the action of the above-mentioned hair growth-modulating substances may affect PK C isoenzymes in cultured dermal papilla cells (DPC), By Western blot a nalysis, protein kinase C alpha, -epsilon, -gamma, -iota, -lambda, and the RACK1 receptor protein were detected in dermal papilla cell cultu res, whereas the isoenzymes delta and mu were expressed only at low le vels and protein kinase C-beta, -theta and -zeta were not present, Aft er PMA stimulation, the PRC alpha, -epsilon, and -gamma were transloca ted from the cytosol to the membrane fraction and subsequently down-re gulated. PRC iota was down-regulated but not translocated, and PKC lam bda and RACK1 mere not affected by PMA; Neither IL-1 beta nor IGF had an effect on PKC or RACK1 expression. We conclude that cultured DPC ex press a distinct PKC isoenzyme pattern and that the PMA-induced growth arrest in cultivated hair follicles may be transmitted via protein ki nases, whereas the effects of IL-1 beta or IGF may be transduced via o ther signal transduction pathways or other cell types.