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A molecular mechanism of integrin crosstalk: alphavbeta3 suppression of calcium/calmodulin-dependent protein kinase
S D Blystone1, S E Slater, M P Williams
1Department of Anatomy and Cell Biology, State University of New York, Health Science Center at Syracuse, Syracuse, New York 13210, USA. blystons@vax.cs.hscsyr.edu
Abstract:
Many cells express more than one integrin receptor for extracellular matrix, and in vivo these receptors may be simultaneously engaged. Ligation of one integrin may influence the behavior of others on the cell, a phenomenon we have called integrin crosstalk. Ligation of the integrin alphavbeta3 inhibits both phagocytosis and migration mediated by alpha5beta1 on the same cell, and the beta3 cytoplasmic tail is necessary and sufficient for this regulation of alpha5beta1. Ligation of alpha5beta1 activates the calcium- and calmodulin-dependent protein kinase II (CamKII). This activation is required for alpha5beta1-mediated phagocytosis and migration. Simultaneous ligation of alphavbeta3 or expression of a chimeric molecule with a free beta3 cytoplasmic tail prevents alpha5beta1-mediated activation of CamKII. Expression of a constitutively active CamKII restores alpha5beta1 functions blocked by alphavbeta3-initiated integrin crosstalk. Thus, alphavbeta3 inhibition of alpha5beta1 activation of CamKII is required for its role in integrin crosstalk. Structure-function analysis of the beta3 cytoplasmic tail demonstrates a requirement for Ser752 in beta3-mediated suppression of CamKII activation, while crosstalk is independent of Tyr747 and Tyr759, implicating Ser752, but not beta3 tyrosine phosphorylation in initiation of the alphavbeta3 signal for integrin crosstalk.
Insights
Integrin crosstalk involves cell receptors influencing each other. Integrin alphavbeta3 inhibits alpha5beta1 functions by blocking CamKII activation, with Ser752 in beta3 crucial for this signaling.
Area of Science:
- Cell Biology
- Molecular Biology
- Biochemistry
Background:
- Cells utilize multiple integrin receptors for extracellular matrix interactions.
- Simultaneous engagement of different integrins can lead to cross-regulatory effects, termed integrin crosstalk.
Purpose of the Study:
- To investigate the mechanism of integrin crosstalk between alphavbeta3 and alpha5beta1.
- To identify the role of calcium- and calmodulin-dependent protein kinase II (CamKII) in this crosstalk.
- To determine the specific domains within the beta3 cytoplasmic tail involved in regulating alpha5beta1 function.
Main Methods:
- Investigated integrin crosstalk using cell-based assays.
- Utilized expression of chimeric molecules and constitutively active CamKII.
- Performed structure-function analysis of the beta3 cytoplasmic tail, focusing on specific serine and tyrosine residues.
Main Results:
- Ligation of integrin alphavbeta3 inhibits phagocytosis and migration mediated by alpha5beta1.
- This inhibition is dependent on the beta3 cytoplasmic tail and involves suppression of CamKII activation.
- Ser752 in the beta3 cytoplasmic tail is critical for alphavbeta3-mediated suppression of CamKII, while Tyr747 and Tyr759 are not involved.
Conclusions:
- Integrin alphavbeta3 regulates alpha5beta1-mediated functions through crosstalk, specifically by inhibiting CamKII activation.
- The Ser752 residue in the beta3 cytoplasmic tail initiates the signal for alphavbeta3-mediated integrin crosstalk.
- These findings elucidate a novel signaling pathway in integrin-mediated cellular processes.