Zhao H, Tian W, Cohen DM. Rottlerin inhibits tonicity-dependent expression and action of TonEBP in a PKCdelta-independent fashion.
Am J Physiol Renal Physiol 2002;
282:F710-7. [PMID:
11880333 DOI:
10.1152/ajprenal.00303.2001]
[Citation(s) in RCA: 17] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
Novel protein kinase C (PKC) isoforms PKCdelta and PKCepsilon have recently been implicated in signaling by hypertonic stress. We investigated the role of the putative PKCdelta inhibitor rottlerin on tonicity-dependent gene regulation. In the renal medullary mIMCD3 cell line, rottlerin blocked tonicity-dependent transcription of a tonicity enhancer (TonE)-driven luciferase reporter gene, as well as tonicity-dependent transcription of the physiological tonicity effector gene aldose reductase, but not urea-dependent transcription. Consistent with these data, rottlerin inhibited tonicity-dependent expression of TonE binding protein (TonEBP) at the mRNA and protein levels. Another inhibitor of both novel and conventional PKC isoforms, GF-109203X, suppressed TonEBP-dependent transcription but failed to influence tonicity-inducible TonEBP expression. Global PKC downregulation with protracted phorbol ester treatment, however, failed to influence tonicity-dependent signaling, arguing against a PKCdelta-dependent mechanism of rottlerin action in this model. In addition, hypertonic stress failed to induce phosphorylation of PKCdelta. Furthermore, in a PC-12 cell model with a comparable degree of tonicity-dependent transcription, constitutive overexpression of dominant negative-acting PKCdelta or PKCepsilon effectively decreased tonicity signaling to extracellular signal-regulated kinase activation, as expected, but failed to influence TonE-dependent transcription. TonE-dependent transcription, however, remained rottlerin sensitive in this PC-12 cell model. In the aggregate, these data indicate that rottlerin dramatically inhibits tonicity-dependent TonEBP expression and TonE-dependent transcription but, despite its reputed mode of action, does so through a PKCdelta-independent pathway.
Collapse