Thrombin increases clusterin mRNA in glomerular epithelial and mesangial cells.

Clusterin, a multifunctional protein with complement blocking activity, and fibrin, a product of thrombin's enzymatic activity, are present in the kidney during acute and chronic renal failure. The role of thrombin in regulating clusterin mRNA in the kidney is not known. The effect of thrombin on clusterin mRNA expression was examined in rat glomerular mesangial and glomerular epithelial cells, and cultured human renal proximal tubular epithelial cells by northern blot. Thrombin (10(-8) M) increased clusterin mRNA levels two- to fourfold in glomerular mesangial, glomerular epithelial, and proximal tubule epithelial cells. This was a specific effect of thrombin receptor activation because peptides corresponding to the tethered ligand of the thrombin receptor were also able to increase clusterin mRNA levels. Epidermal growth factor, insulin-like growth factor-1, and transforming growth factor-beta 1 had little or no effect on clusterin mRNA levels. The protein kinase C inhibitor RO-32-0432 (1 microM) inhibited the thrombin-induced increase in clusterin mRNA, suggesting that thrombin receptor activation may regulate renal clusterin mRNA levels through protein kinase C.

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The co-mitogenic combination of transforming growth factor β1 and bombesin protects protein kinase C-δ from late-phase down-regulation, despite synergy in diacylglycerol accumulation

Biochemical Journal ◽

10.1042/bj3180519 ◽

1996 ◽

Vol 318 (2) ◽

pp. 519-525 ◽

Cited By ~ 12

Author(s):

Andrée R. OLIVIER ◽

Gurdip HANSRA ◽

Trevor R. PETTITT ◽

Michael J. O. WAKELAM ◽

Peter J. PARKER

Keyword(s):

Protein Kinase C ◽

Growth Factor ◽

Protein Kinase ◽

Transforming Growth Factor ◽

Late Phase ◽

Flow Cytometric Analysis ◽

Transforming Growth Factor Β1 ◽

Mrna Levels ◽

Down Regulation ◽

Kinase C

Bombesin induces the down-regulation of protein kinase C-Δ (PKC-Δ) and PKC-ϵ in Swiss 3T3 cells. Simultaneous addition of transforming growth factor β1 (TGFβ1) selectively blocks PKC-Δ down-regulation at mid-S-phase, whereas PKC-ϵ levels continue to decline. Northern blot analysis shows that PKC-ϵ levels could be controlled in part at the level of transcription; PKC-Δ mRNA levels remained constant at these later times. Bombesin induces a sustained elevation of some species of diacylglycerol (DAG), consistent with the observed loss of PKC-Δ and PKC-ϵ. Interestingly, the combination of bombesin and TGF-β1 produces an even greater DAG response. Flow cytometric analysis demonstrates that bombesin induces only 15% of the cells to enter the cell cycle, in contrast to the combination of TGFβ1 plus bombesin which induces 75–80% of the cells to progress through the cycle. The protection of PKC-Δ from down-regulation under conditions of sustained DAG elevation correlates with the mitogenic response and implies that the down-regulation process itself is regulated. Consistent with this, it is demonstrated that bombesin plus TGFβ1 protects PKC-Δ from phorbol ester-induced down-regulation.

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