RELATIONSHIP BETWEEN ORNITHINE DECARBOXYLASE AND CYTOSKELETAL ORGANIZATION IN CULTURED HUMAN KERATINOCYTES - CELLULAR-RESPONSES TO PHORBOL ESTERS, CYTOCHALASINS, AND ALPHA-DIFLUOROMETHYLORNITHINE

Changes in cell shape occur during the cell cycle and influence cell p roliferation and differentiation. In order to study how altered cell p roliferation and cell shape are interrelated, we have studied ornithin e decarboxylase (ODC) regulation in cultured normal human epidermal ke ratinocytes (NHEK). Cytoskeletal disrupters have been reported to modu late regulation of ODC; the products of ODC, the polyamines, influence actin polymerization rates in vitro, and polyamine auxotrophs have pr ofoundly disrupted cytoskeletons. Therefore, altered ODC levels could be involved in signaling changes in cell shape and an intact cytoskele ton could transduce signals to regulate ODC levels, We had previously observed that the phorbol ester 12-O-tetradecanoylphorbol-13-acetate ( TPA), which profoundly alters cell shape, markedly suppresses ODC bios ynthesis in NHEK solely at posttranscriptional/protein synthesis level s, TPA treatment caused NHEK to rapidly assume a rounded morphology th at was accompanied by a change in actin organization, as determined by rhodamine-phalloidin labeling, Immunolocalization of ODC showed a per inuclear/nuclear distribution in untreated NHEK and a more diffuse pat tern after TPA treatment that was apparent within 15-30 min, Changes i n ODC enzyme activity are not significant until 60 min after TPA treat ment, NHEK treated with cytochalasin B or D to inhibit actin polymeriz ation exhibited a diffuse ODC localization that could be reversed by r emoval of the cytochalasin; inhibition of ODC by alpha-difluoromethylo rnithine caused a diffuse ODC localization, All treatments resulted in cytoskeletal remodeling, These data are the first evidence for a dist inct subcellular localization for ODC and suggest that changes in ODC localization may be an initial step in regulation of ODC activity, Fur thermore, changes in ODC activity cause an altered cytoskeleton, sugge sting one means by which to the growth regulatory signals can be trans duced cytoskeleton from various signaling pathways. (C) 1995 Academic Press, Inc.