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Signal transduction through the vasoactive intestinal peptide receptor stimulates phosphorylation of the tyrosine
1Department of Ophthalmology, University of Maryland, Baltimore 21201.
Abstract:
The present study demonstrates that signal transduction through a receptor lacking intrinsic tyrosine protein kinase activity involves a rapid and potent phosphorylation of a non-receptor tyrosine protein kinase in the membranes. Vasoactive intestinal peptide (VIP) stimulates phosphorylation of a membrane protein with a M.W. of 56 KD (pp60) in the cultured chick embryonic retinal pigment epithelium. VIP stimulates phosphorylation of the pp60 with such efficiency and potency that the maximal phosphorylation has been observed at the earliest time (3 minutes at 1 x 10(-6)M VIP) and the lowest concentration (1 x 10(-11)M for 20 minutes) examined. Western blot analysis with a monoclonal antibody anti-pp60src (GD11, Parsons et al., J. Virol. 51, 272-282, 1984) indicates that the pp60 is the pp60c-src, a normal cell oncogene product with intrinsic tyrosine protein kinase activity.
Insights
Vasoactive intestinal peptide (VIP) rapidly activates a key cell signaling protein, pp60c-src, in retinal pigment epithelium. This non-receptor tyrosine kinase phosphorylation is a potent early event in VIP receptor signal transduction.
Area of Science:
- Cell Biology
- Molecular Biology
- Biochemistry
Background:
- Signal transduction pathways are crucial for cellular communication.
- Receptors lacking intrinsic tyrosine kinase activity often rely on associated kinases.
- Vasoactive intestinal peptide (VIP) is a neuropeptide with diverse physiological roles.
Purpose of the Study:
- To investigate the mechanism of signal transduction initiated by VIP.
- To identify the specific tyrosine protein kinase involved in VIP signaling.
- To characterize the kinetics and potency of VIP-induced kinase activation.
Main Methods:
- Cell culture of chick embryonic retinal pigment epithelium.
- Stimulation with varying concentrations and time courses of VIP.
- Western blot analysis using anti-pp60src monoclonal antibody.
Main Results:
- VIP rapidly and potently stimulates the phosphorylation of a 56 kDa membrane protein (pp60).
- Maximal phosphorylation occurred within 3 minutes at 1 x 10(-6)M VIP.
- The phosphorylated protein was identified as pp60c-src, a tyrosine kinase.
- VIP signaling involves a non-receptor tyrosine kinase.
Conclusions:
- VIP receptor signaling activates the non-receptor tyrosine kinase pp60c-src.
- This activation is a rapid and highly potent early event.
- pp60c-src plays a significant role in VIP-mediated signal transduction in retinal pigment epithelium.