scholarly journals The sites of phosphorylation by protein kinase C and an intact SH2 domain are required for the enhanced response to beta-adrenergic agonists in cells overexpressing c-src.

1993 ◽  
Vol 13 (4) ◽  
pp. 2391-2400 ◽  
Author(s):  
J S Moyers ◽  
A H Bouton ◽  
S J Parsons

Previously we demonstrated that C3H10T1/2 murine fibroblasts overexpressing avian c-src exhibit elevated levels of cyclic AMP (cAMP) in response to beta-adrenergic agonists compared with that in control cells and that this enhanced response requires c-src kinase activity (W. A. Bushman, L. K. Wilson, D. K. Luttrell, J. S. Moyers, and S. J. Parsons, Proc. Natl. Acad. Sci. USA 87:7462-7466, 1990). However, it is not yet known which components of the beta-adrenergic receptor pathway, if any, interact with pp60c-src. It has recently been shown that immune complexes of pp60c-src phosphorylate recombinant G alpha proteins in vitro to stoichiometric levels, resulting in alterations of GTP binding and GTPase activity (W. P. Hausdorff, J. A. Pitcher, D. K. Luttrell, M. E. Linder, H. Kurose, S. J. Parsons, M. G. Caron, and R. J. Lefkowitz, Proc. Natl. Acad. Sci. USA 89:5720-5724, 1992), raising the possibility that the Gs alpha protein may be an in vivo target for the interaction with pp60c-src. To further characterize the involvement of pp60c-src in the beta-adrenergic signalling pathway, we have overexpressed, in 10T1/2 cells, pp60c-src containing mutations in several domains which are believed to be important for signalling processes. In this study we show that the sites of phosphorylation by protein kinase C (PKC) (Ser-12 and Ser-48) as well as the SH2 region of pp60c-src are required for the enhanced response of c-src overexpressors to beta-agonist stimulation. Mutation at the site of myristylation (Gly-2) results in a decrease in the enhanced response, while mutation at the site of phosphorylation by cAMP-dependent protein kinase (Ser-17) has no effect. Two-dimensional phosphotryptic analyses indicate that phosphorylation on Ser-12 and Ser-48 in unstimulated cells is associated with the ability of overexpressed pp60c-src to potentiate beta-adrenergic signalling. Cells overexpressing wild-type c-src also exhibit enhanced cAMP accumulation upon treatment with cholera toxin, an effect that is abated in cells overexpressing pp60c-src defective in the kinase or SH2 domains or altered at the sites of phosphorylation by PKC. These studies provide the first evidence for the physiological significance of the pp60c-src sites of PKC phosphorylation. In addition, they show that the SH2, Ser-12/48, and myristylation regions may be important for efficient interaction of pp60c-src with components of the beta-adrenergic pathway. Our data also support the possibility that the Gs alpha protein may be an in vivo target for alteration by pp60c-src.

1993 ◽  
Vol 13 (4) ◽  
pp. 2391-2400
Author(s):  
J S Moyers ◽  
A H Bouton ◽  
S J Parsons

Previously we demonstrated that C3H10T1/2 murine fibroblasts overexpressing avian c-src exhibit elevated levels of cyclic AMP (cAMP) in response to beta-adrenergic agonists compared with that in control cells and that this enhanced response requires c-src kinase activity (W. A. Bushman, L. K. Wilson, D. K. Luttrell, J. S. Moyers, and S. J. Parsons, Proc. Natl. Acad. Sci. USA 87:7462-7466, 1990). However, it is not yet known which components of the beta-adrenergic receptor pathway, if any, interact with pp60c-src. It has recently been shown that immune complexes of pp60c-src phosphorylate recombinant G alpha proteins in vitro to stoichiometric levels, resulting in alterations of GTP binding and GTPase activity (W. P. Hausdorff, J. A. Pitcher, D. K. Luttrell, M. E. Linder, H. Kurose, S. J. Parsons, M. G. Caron, and R. J. Lefkowitz, Proc. Natl. Acad. Sci. USA 89:5720-5724, 1992), raising the possibility that the Gs alpha protein may be an in vivo target for the interaction with pp60c-src. To further characterize the involvement of pp60c-src in the beta-adrenergic signalling pathway, we have overexpressed, in 10T1/2 cells, pp60c-src containing mutations in several domains which are believed to be important for signalling processes. In this study we show that the sites of phosphorylation by protein kinase C (PKC) (Ser-12 and Ser-48) as well as the SH2 region of pp60c-src are required for the enhanced response of c-src overexpressors to beta-agonist stimulation. Mutation at the site of myristylation (Gly-2) results in a decrease in the enhanced response, while mutation at the site of phosphorylation by cAMP-dependent protein kinase (Ser-17) has no effect. Two-dimensional phosphotryptic analyses indicate that phosphorylation on Ser-12 and Ser-48 in unstimulated cells is associated with the ability of overexpressed pp60c-src to potentiate beta-adrenergic signalling. Cells overexpressing wild-type c-src also exhibit enhanced cAMP accumulation upon treatment with cholera toxin, an effect that is abated in cells overexpressing pp60c-src defective in the kinase or SH2 domains or altered at the sites of phosphorylation by PKC. These studies provide the first evidence for the physiological significance of the pp60c-src sites of PKC phosphorylation. In addition, they show that the SH2, Ser-12/48, and myristylation regions may be important for efficient interaction of pp60c-src with components of the beta-adrenergic pathway. Our data also support the possibility that the Gs alpha protein may be an in vivo target for alteration by pp60c-src.


1991 ◽  
Vol 261 (2) ◽  
pp. L172-L177 ◽  
Author(s):  
A. Paul ◽  
M. Mergey ◽  
D. Veissiere ◽  
B. Hermelin ◽  
G. Cherqui ◽  
...  

We recently reported that cultured gland serous cells release chondroitin sulfate proteoglycans (CSPGs) in response to beta-adrenergic agonists. In this study, we analyzed this regulatory pathway and other cellular mechanisms responsible for CSPG secretion. We show the following. 1) Isoproterenol increased CSPG secretion in a concentration-dependent manner, with maximal stimulation (50%) obtained at 10(-5) M; at this concentration, the beta-agonist also stimulated protein kinase A (PKA) by 50%, whereas it increased cellular adenosine 3',5'-cyclic monophosphate (cAMP) content by 300%. 2) Phenylephrine (10(-5) M), 4 beta-phorbol 12 beta-myristate 13 alpha-acetate (1.6 x 10(-7) M), and A23187 (10(-6) M) also stimulated CSPG secretion; this stimulation was concomitant with protein kinase C (PKC) translocation from cytosol to membrane, was blocked by sphingosine (2 x 10(-5) M), and was additive with that elicited by isoproterenol. 3) All PKC activators potentiated the isoproterenol-induced increased in cAMP accumulation without modifying the activation of PKA elicited by the beta-agonist. Our results indicate that although the signaling pathways triggered by alpha- and beta-adrenergic agonists converge at the level of adenylate cyclase in tracheal serous cells, PKA and PKC independently regulate CSPG secretion.


2000 ◽  
Vol 33 (4) ◽  
pp. 601-608 ◽  
Author(s):  
Shwu-Bin Lin ◽  
Li-Ching Wu ◽  
Siao-Ling Huang ◽  
Hui-Lun Hsu ◽  
Sung-Hwa Hsieh ◽  
...  

1990 ◽  
Vol 122 (3) ◽  
pp. 403-408
Author(s):  
Ph. Touraine ◽  
P. Birman ◽  
F. Bai-Grenier ◽  
C. Dubray ◽  
F. Peillon ◽  
...  

Abstract In order to investigate whether a calcium channel blocker could modulate the protein kinase C activity in normal and estradiol pretreated rat pituitary, female Wistar rats were treated or not (controls) with ± PN 200-110 (3 mg · kg−1 · day−1, sc) for 8 days or with estradiol cervical implants for 8 or 15 days, alone or in combination with PN 200-110 the last 8 days. Estradiol treatment induced a significant increase in plasma prolactin levels and pituitary weight. PN 200-110 administered to normal rats did not modify these parameters, whereas it reduced the effects of the 15 days estradiol treatment on prolactin levels (53.1 ± 4.9 vs 95.0 ±9.1 μg/l, p<0.0001) and pituitary weight (19.9 ± 0.4 vs 23.0 ± 0.6 mg, p <0.001), to values statistically comparable to those measured after 8 days of estradiol treatment. PN 200-110 alone did not induce any change in protein kinase C activity as compared with controls. In contrast, PN 200-110 treatment significantly counteracted the large increase in soluble activity and the decrease in the particulate one induced by estradiol between day 8 and day 15. We conclude that PN 200-110 opposed the stimulatory effects of chronic in vivo estradiol treatment on plasma prolactin levels and pituitary weight and that this regulation was related to a concomitant modulation of the protein kinase C activity.


1993 ◽  
Vol 207 (1) ◽  
pp. 68-73 ◽  
Author(s):  
Kirstine A. Knox ◽  
Gerald D. Johnson ◽  
John Gordon

2016 ◽  
Vol 310 (9) ◽  
pp. F821-F831 ◽  
Author(s):  
Da Xu ◽  
Haoxun Wang ◽  
Qiang Zhang ◽  
Guofeng You

Human organic anion transporter 1 (hOAT1) expressed at the membrane of the kidney proximal tubule cells mediates the body disposition of a diverse array of clinically important drugs, including anti-HIV therapeutics, antitumor drugs, antibiotics, antihypertensives, and antiinflammatories. Therefore, understanding the regulation of hOAT1 will provide significant insights into kidney function and dysfunction. We previously established that hOAT1 transport activity is inhibited by activation of protein kinase C (PKC) through accelerating hOAT1 internalization from cell surface into intracellular endosomes and subsequent degradation. We further established that PKC-induced hOAT1 ubiquitination is an important step preceding hOAT1 internalization. In the current study, we identified two closely related E3 ubiquitin ligases, neural precursor cell expressed, developmentally downregulated 4-1 and 4-2 (Nedd4-1 and Nedd4-2), as important regulators for hOAT1: overexpression of Nedd4-1 or Nedd4-2 enhanced hOAT1 ubiquitination, reduced the hOAT1 amount at the cell surface, and suppressed hOAT1 transport activity. In further exploring the relationship among PKC, Nedd4-1, and Nedd4-2, we discovered that PKC-dependent changes in hOAT1 ubiquitination, expression, and transport activity were significantly blocked in cells transfected with the ligase-dead mutant of Nedd4-2 (Nedd4-2/C821A) or with Nedd4-2-specific siRNA to knockdown endogenous Nedd4-2 but not in cells transfected with the ligase-dead mutant of Nedd4-1 (Nedd4-1/C867S) or with Nedd4-1-specific siRNA to knockdown endogenous Nedd4-1. In conclusion, this is the first demonstration that both Nedd4-1 and Nedd4-2 are important regulators for hOAT1 ubiquitination, expression, and function. Yet they play distinct roles, as Nedd4-2 but not Nedd4-1 is a critical mediator for PKC-regulated hOAT1 ubiquitination, expression, and transport activity.


2004 ◽  
Vol 89 (5) ◽  
pp. 1119-1125 ◽  
Author(s):  
Orit Bar-Am ◽  
Merav Yogev-Falach ◽  
Tamar Amit ◽  
Yotam Sagi ◽  
Moussa B. H. Youdim

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