title: RhoA-dependent murine prostate cancer cell proliferation and apoptosis: role of protein kinase Czeta.
abstract: We previously showed that RhoA played an important role in the proliferation of murine We prostate cancer (TRAMP) cells (P. M. Ghosh et al., Oncogene, 18: 4120-4130, 1999). Untransfected TRAMP cells as well as those expressing constitutively active RhoA (Q63L) mutant protein (Q63L cells) were highly proliferative. In contrast, TRAMP cells expressing dominant-negative RhoA (T19N) mutant protein (T19N cells) were slow growing. In this study, we showed, in addition, that T19N cells displayed reduced rates of apoptotic cell death in response to serum deprivation, compared with TRAMP and Q63L cells, and we studied the mechanisms of the effects of RhoA on TRAMP cell proliferation and apoptosis. Both proliferation and apoptosis of TRAMP and Q63L cells were dependent on the activation of phosphatidylinositol 3-kinase (PI3K). The ubiquitous mitogen-activated Ser/Thr kinase, p70S6 kinase, a downstream effector of PI3K, was overexpressed in TRAMP and Q63L cells. Another PI3K effector, the cell survival protein Akt, displayed increased activity in T19N cells, which did not express active RhoA, compared with TRAMP and Q63L cells. The atypical protein kinase C (PKC) isoform PKCzeta, which is downstream of PI3K, was activated in cells expressing active RhoA. In addition, expression of constitutively activated PKCzeta in TRAMP cells enhanced proliferation and p70S6 kinase phosphorylation, whereas the inhibition of PKCzeta activation resulted in activation of Akt and enhanced cell survival. Thus, the effects of RhoA on TRAMP cell proliferation and apoptosis may be mediated by PKCzeta.
authors: Department of Surgery, University of Texas Health Science Center, San Antonio, Texas, USA. ghosh@uthscsa.edu
authors: Paramita M
authors: PM
authors: Ghosh
authors: Roble
authors: R
authors: Bedolla
authors: Margharita
authors: M
authors: Mikhailova
authors: Jeffrey I
authors: JI
authors: Kreisberg
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000502:physiology; D002455:Cell Division / Q000502:physiology; D002470:Cell Survival / Q000502:physiology; D004789:Enzyme Activation; D008297:Male; D051379:Mice; D008822:Mice, Transgenic; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D010766:Phosphorylation; D011471:Prostatic Neoplasms / Q000201:enzymology* / Q000473:pathology*; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism / Q000502:physiology*; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt; D019893:Ribosomal Protein S6 Kinases / Q000096:biosynthesis / Q000378:metabolism; D020742:rhoA GTP-Binding Protein / Q000037:antagonists & inhibitors / Q000096:biosynthesis / Q000502:physiology*; D000099221:Protein Kinase C zeta
chemical_list: D019869:Phosphatidylinositol 3-Kinases; D011493:Protein Kinase C; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins; D051057:Proto-Oncogene Proteins c-akt; D019893:Ribosomal Protein S6 Kinases; D020742:rhoA GTP-Binding Protein; D000099221:Protein Kinase C zeta