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Inhibition of p130cas tyrosine phosphorylation by calyculin A
1Department of Biology, Tanabe Research Laboratories, San Diego, California, USA.
Abstract:
P130cas is a dominant tyrosine phosphorylated protein in v-src-and v-crk-transformed cells. Tyrosine phosphorylation also occurs in response to integrin-mediated cell adhesion. P130cas has a unique structure with multiple SH2 and SH3 binding sites, which makes it a candidate docking protein that might be involved in several signal transduction pathways. Little is known about how p130cas itself is regulated. In this report we present evidence that tyrosine phosphorylated p130cas was rapidly dephosphorylated in several lymphatic cell lines after treatment with calyculin A, a serine/threonine phosphatase inhibitor. A similar result was obtained with okadaic acid, but higher concentrations and longer incubation times were required. Constitutive phosphorylation as well as receptor-cross linking-induced p130cas phosphorylation was inhibited. Furthermore, the p130cas-Crk association was disrupted by treatment of cells with calyculin A. However, the p130cas-Lyn association was not affected. These results suggest that calyculin A specifically affects SH2 domain-mediated protein-protein interactions and that Lyn does not bind to a susceptible SH2 domain. Furthermore, the data presented is consistent with the existence of a calyculin A-sensitive phosphatase or tyrosine kinase that may be a critical regulator of p130cas tyrosine phosphorylation.
Insights
Calyculin A rapidly dephosphorylates p130cas, a key protein in cell signaling. This suggests a calyculin A-sensitive regulator controls p130cas tyrosine phosphorylation and protein interactions.
Area of Science:
- Cellular Biology
- Molecular Biology
- Signal Transduction
Background:
- P130cas is a major tyrosine-phosphorylated protein in transformed cells and upon integrin-mediated adhesion.
- Its structure suggests a role as a docking protein in multiple signaling pathways.
- Regulation of p130cas tyrosine phosphorylation remains largely uncharacterized.
Purpose of the Study:
- To investigate the regulation of p130cas tyrosine phosphorylation.
- To identify potential phosphatases or kinases involved in p130cas regulation.
- To explore the impact of phosphatase inhibitors on p130cas phosphorylation and interactions.
Main Methods:
- Treatment of lymphatic cell lines with calyculin A and okadaic acid (serine/threonine phosphatase inhibitors).
- Analysis of p130cas tyrosine phosphorylation levels.
- Investigation of p130cas interactions with Crk and Lyn proteins.
Main Results:
- Calyculin A rapidly dephosphorylated tyrosine-phosphorylated p130cas in lymphatic cells.
- Okadaic acid also induced dephosphorylation, but required higher concentrations and longer incubation.
- Calyculin A disrupted p130cas-Crk association but not p130cas-Lyn association.
- These findings suggest a calyculin A-sensitive phosphatase or kinase regulates p130cas.
Conclusions:
- Tyrosine phosphorylation of p130cas is regulated by a calyculin A-sensitive mechanism.
- Calyculin A specifically impacts SH2 domain-mediated interactions, affecting p130cas-Crk binding.
- Lyn binding to p130cas does not involve a calyculin A-sensitive SH2 domain.