CGP 41251 a Novel Protein Kinase Inhibitor with in vitro Selectivity for Protein Kinase C, Strongly Inhibits Immunological Activation of Human Skin Mast Cells and Human Basophils

Pharmacology ◽  
1993 ◽  
Vol 47 (3) ◽  
pp. 200-208 ◽  
Author(s):  
Ulrich Amon ◽  
Esther von Stebut ◽  
Natarajan Subramanian ◽  
Helmut H. Wolff
Keyword(s):  
Protein Kinase C ◽  
Mast Cells ◽  
Protein Kinase ◽  
Human Skin ◽  
Kinase Inhibitor ◽  
Immunological Activation ◽  
Kinase C ◽  
Human Basophils ◽  
Novel Protein

Protein kinase C–catalyzed phosphorylation of an inhibitory phosphoprotein of myosin phosphatase is involved in human platelet secretion

Blood ◽  
2001 ◽  
Vol 97 (12) ◽  
pp. 3798-3805 ◽  
Author(s):  
Yasuyuki Watanabe ◽  
Masaaki Ito ◽  
Yoshiyuki Kataoka ◽  
Hideo Wada ◽  
Mutsumi Koyama ◽  
...  
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Kinase Inhibitor ◽  
Rho Kinase ◽  
Myosin Phosphatase ◽  
Kinase C ◽  
Atp Secretion ◽  
Mlc20 Phosphorylation ◽  
Platelet Secretion

Protein kinase C (PKC)–potentiated inhibitory phosphoprotein of myosin phosphatase (CPI) was detected in human platelets. Like smooth muscle CPI-17, in vitro phosphorylation of platelet CPI by PKC inhibited the activity of myosin phosphatase containing the PP1δ catalytic subunit and the 130-kd myosin-binding subunit (MBS). Treatment of intact platelets with thrombin or the stable thromboxane A2 analog STA2 resulted in increased phosphorylation of both CPI and MBS at Thr-696, whereas phorbol myristate acetate (PMA) and the Ca++ ionophore ionomycin only induced CPI phosphorylation. PMA induced slow adenosine triphosphate (ATP) secretion of fura 2–loaded platelets with no change in cytosolic Ca++. The PMA-induced increase in CPI phosphorylation preceded phosphorylation of 20-kd myosin light chain (MLC20) at Ser-19 and ATP secretion. The PKC inhibitor, GF109203X, inhibited PMA-induced phosphorylation of CPI and MLC20 with similar IC50 values. These findings suggest that the activation of PKC by PMA induces MLC20phosphorylation by inhibiting myosin phosphatase through phosphorylation of CPI. STA2-induced MLC20phosphorylation was also diminished but not abolished by GF109203X, even at high concentrations that completely inhibited STA2-induced CPI phosphorylation. A combination of the Rho-kinase inhibitor Y-27632 and GF109203X led to a further decrease in STA2-induced MLC20 phosphorylation, mainly because of a significant inhibition of MBS phosphorylation at Thr-696. Inhibition of STA2-induced ATP release by Y-27632, GF109203X, or both appeared to correlate with the extent of MLC20 phosphorylation. Thus, CPI phosphorylation by PKC may participate in inhibiting myosin phosphatase, in addition to the Rho-kinase–mediated regulation of myosin phosphatase, during agonist-induced platelet secretion.

scholarly journals Lambda-interacting protein, a novel protein that specifically interacts with the zinc finger domain of the atypical protein kinase C isotype lambda/iota and stimulates its kinase activity in vitro and in vivo.

1996 ◽  
Vol 16 (1) ◽  
pp. 105-114 ◽  
Author(s):  
M T Diaz-Meco ◽  
M M Municio ◽  
P Sanchez ◽  
J Lozano ◽  
J Moscat
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Zinc Finger ◽  
Zinc Finger Domain ◽  
Interacting Protein ◽  
Kinase C ◽  
Novel Protein

The members of the atypical subfamily of protein kinase C (PKC) show dramatic structural and functional differences from other PKC isotypes. Thus, in contrast to the classical or novel PKCs, they are not activated by diacylglycerol or phorbol esters. However, the atypical PKCs are the target of important lipid second messengers such as ceramide, phosphatidic acid, and 3'-phosphoinositides. The catalytic and pseudosubstrate sequences in the two atypical PKCs (lambda/iota PKC and zeta PKC) are identical but are significantly different from those of conventional or novel PKCs. It has been shown that microinjection of a peptide with the sequence of the pseudosubstrate of the atypical PKC isotypes but not of alpha PKC or epsilon PKC dramatically inhibited maturation and NF-kappa B activation in Xenopus oocytes, as well as reinitiation of DNA synthesis in quiescent mouse fibroblasts. This indicates that either or both atypical isoforms are important in cell signalling. Besides the pseudosubstrate, the major differences in the sequence between lambda/iota PKC and zeta PKC are located in the regulatory domain. Therefore, any functional divergence between the two types of atypical PKCs will presumably reside in that region. We report here the molecular characterization of lambda-interacting protein (LIP), a novel protein that specifically interacts with the zinc finger of lambda/iota PKC but not zeta PKC. We show in this paper that this interaction is detected not only in vitro but also in vivo, that LIP activates lambda/iota PKC but not zeta PKC in vitro and in vivo, and that this interaction is functionally relevant. Thus, expression of LIP leads to the transactivation of a kappa B-dependent promoter in a manner that is dependent on lambda/iota PKC. To our knowledge, this is the first report on the cloning and characterization of a protein activator of a PKC that binds to the zinc finger domain, which has so far been considered a site for binding of lipid modulators. The fact that LIP binds to lambda/iota PKC but not to the highly related zeta PKC isoform suggests that the specificity of the activation of the members of the different PKC subfamilies will most probably be accounted for by proteins like LIP rather than by lipid activators.

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