scholarly journals Regulation of capacitative calcium influx in cultured human mesangial cells: roles of protein kinase C and calmodulin.

1996 ◽  
Vol 7 (7) ◽  
pp. 983-990
Author(s):  
P Menè ◽  
F Pugliese ◽  
G A Cinotti
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Mesangial Cells ◽  
Calcium Influx ◽  
Resting Cells ◽  
Cellular Mechanisms ◽  
Direct Role ◽  
Human Mesangial Cells ◽  
Kinase C

Sustained Ca2+ influx follows discharge of intracellularly stored Ca2+ in a variety of cell types previously equilibrated in Ca(2+)-free media, including cultured human mesangial cells. This Ca2+ influx pathway has been referred to as capacitative Ca2+ entry or Ca2+ release-activated Ca2+ influx (iCRAC). This study investigated two cellular mechanisms potentially controlling iCRAC in human mesangial cells, protein kinase C (PKC), a key signalling kinase activated by vasoconstrictors that release Ca2+ from internal stores, and calmodulin, a Ca(2+)-binding protein that may couple Ca2+ release to the putative channel(s). The PKC activator phorbol myristate acetate (PMA) dose-dependently inhibited both Ca2+ influx in resting cells and iCRAC, assessed by microfluorometry in fura-2-loaded monolayers, when added before or after 1 uM angiotensin II (AngII) (Ca2+ influx at 1 mM (Ca2+)e +278 +/- 56%/+80 +/- 8%, at 10 mM + 473 +/- 59%/+250 +/- 24% (Ca2+)e, -/+ PMA, respectively, P < 0.05). PMA did not affect 5 uM ionomycin-induced iCRAC, possibly because it downregulated Ca2+ release by AngII but not by ionomycin, suggesting a key role of released Ca2+ in triggering subsequent Ca2+ influx. This was confirmed by buffering the (Ca2+)i elevation induced by AngII with intracellularly trapped 1,2-bis-(0-Aminophenoxy)-ethane-N,N,N',N'-tetraacetic acid (BAPTA), which abolished any subsequent iCRAC. Moreover, the calmodulin inhibitors calmidazolium (10 uM), trifluoperazine (0.1 mM), or W-7 (0.1 mM) significantly inhibited AngII- or ionomycin-activated iCRAC (+106 +/- 38/229 +/- 53, +58 +/- 9/195 +/- 29, +161 +/- 38/180 +/- 40% at 1/10 mM (Ca2+)e, all P < 0.05), but did not affect basal Ca2+ entry, consistent with a direct role of cytoplasmic Ca2+ in the regulation of ion gating. These results indicate that iCRAC is under the control of both PKC and calmodulin, and that the site of regulation is distal to the emptying of Ca2+ stores. iCRAC may represent a key mechanism for the control of Ca(2+)-regulated mesangial functions.

Mechanical stretch/relaxation of cultured rat mesangial cells induces protooncogenes and cyclooxygenase

1994 ◽  
Vol 267 (2) ◽  
pp. C482-C490 ◽  
Author(s):  
Y. Akai ◽  
T. Homma ◽  
K. D. Burns ◽  
T. Yasuda ◽  
K. F. Badr ◽  
...  
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Mesangial Cells ◽  
Calcium Influx ◽  
Regulation Of Gene Expression ◽  
Calcium Content ◽  
Mechanical Stretch ◽  
Glomerular Mesangial Cells ◽  
Cell Functions ◽  
Kinase C

In cultured rat glomerular mesangial cells, continuous cycles of stretching and relaxation (stretch/relaxation) stimulate cell proliferation, protein synthesis, and prostaglandin production. We examined regulation of gene expression that may underlie these alterations in cell functions. Stretch/relaxation caused time-dependent induction of the immediate early genes, c-fos and zif 268/egr-1, with maximal increases occurring between 15 and 30 min. The mitogen-inducible prostaglandin G2/H2 synthase (PGH2S-2) gene was also induced within 30 min of stretch/relaxation, with concomitant increases in the immunoreactive PGH2S-2 protein. These gene inductions were preceded by transient translocation of protein kinase C activity from cytosol to membrane as well as by increases in 45Ca2+ uptake and total cellular calcium content. The stretch/relaxation-induced expression was suppressed by protein kinase C inhibition, whereas less profound inhibition was observed with inhibition of calcium influx in low (100 nM) calcium buffer. These findings indicate that in mesangial cells mechanical stress induces expression of the protooncogenes and the mitogen-inducible cyclooxygenase primarily through protein kinase C-dependent mechanisms.

Alterations in basal protein kinase C activity modulate renal afferent arteriolar myogenic reactivity

1998 ◽  
Vol 275 (2) ◽  
pp. H467-H475 ◽  
Author(s):  
C. Adam Kirton ◽  
Rodger Loutzenhiser
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Rat Kidney ◽  
K Channel ◽  
Delayed Rectifier ◽  
Afferent Arteriole ◽  
Direct Role ◽  
Kinase C

Myogenic vasoconstriction of the renal afferent arteriole contributes to the autoregulation of renal blood flow, glomerular filtration rate, and glomerular capillary pressure (PGC). The reactivity of the afferent arteriole to pressure and the efficiency of PGC control are subject to physiological and pathophysiological alterations, but the determinants of the myogenic response of this vessel are largely unknown. We used the in vitro perfused hydronephrotic rat kidney to investigate the role of protein kinase C (PKC) in the control of this response. Inhibition of PKC by 1 μM chelerythrine attenuated myogenic reactivity but did not affect the afferent arteriole vasoconstrictor response to KCl (35 mM)-induced depolarization. Low concentrations of phorbol ester (10 nM phorbol 12-myristate 13-acetate) and low levels of ANG II or endothelin-1 (3 pM) potentiated myogenic vasoconstriction without affecting basal afferent arteriolar diameters. These actions were blocked by 1 μM chelerythrine, suggesting a PKC-dependent mechanism. Finally, although PKC inhibition attenuated basal myogenic responses, full reactivity to pressure was restored by 1 mM 4-aminopyridine, a pharmacological inhibitor of delayed rectifier K channels, which are known to be modulated by PKC. The ability of 4-aminopyridine to circumvent the effects of PKC inhibition militates against a direct role of PKC in myogenic signaling. We interpret these observations as indicating that basal PKC activity is an important determinant of myogenic reactivity in the renal afferent arteriole. However, PKC activation does not appear to play an obligate role in myogenic signaling in this vessel. We suggest that basal PKC activity directly modulates voltage-gated K channel activity, thereby indirectly affecting myogenic reactivity.

Endothelin stimulates phosphatidic acid formation in cultured rat mesangial cells: Role of a protein kinase C-regulated phospholipase D

1992 ◽  
Vol 150 (3) ◽  
pp. 578-585 ◽  
Author(s):  
Mark Kester ◽  
Michael S. Simonson ◽  
R. Guy McDermott ◽  
Elisabetta Baldi ◽  
Michael J. Dunn
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Phosphatidic Acid ◽  
Phospholipase D ◽  
Mesangial Cells ◽  
Acid Formation ◽  
Kinase C
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