Integrins Regulate Microtubule Nucleating Activity of Centrosome through Mitogen-activated Protein Kinase/Extracellular Signal-regulated Kinase Kinase/Extracellular Signal-regulated Kinase (MEK/ERK) Signaling

• Published in: The Journal of biological chemistry 2012-01, Vol.287 (4), p.2520-2530
• Main Authors: Colello, Diane, Mathew, Shomita, Ward, Rachel, Pumiglia, Kevin, LaFlamme, Susan E.
• Format: Article
• Language: English
• Subjects: Animals; Cell Biology; Centrosome; Centrosome - metabolism; CHO Cells; Cricetinae; Cricetulus; ERK; Extracellular Matrix; Extracellular Signal-Regulated MAP Kinases - genetics; Extracellular Signal-Regulated MAP Kinases - metabolism; Humans; Integrin; Integrin beta1 - genetics; Integrin beta1 - metabolism; MAP Kinase Kinase Kinases - genetics; MAP Kinase Kinase Kinases - metabolism; MAP Kinase Signaling System - physiology; Microtubules; Microtubules - genetics; Microtubules - metabolism; Phosphatidylinositol 3-Kinases - genetics; Phosphatidylinositol 3-Kinases - metabolism; Proto-Oncogene Proteins c-akt - genetics; Proto-Oncogene Proteins c-akt - metabolism; Proto-Oncogene Proteins c-raf - genetics; Proto-Oncogene Proteins c-raf - metabolism; Src; Tubulin - genetics; Tubulin - metabolism
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M111.254128

Microtubule nucleation is an essential step in the formation of the microtubule cytoskeleton. We recently showed that androgen and Src promote microtubule nucleation and γ-tubulin accumulation at the centrosome. Here, we explore the mechanisms by which androgen and Src regulate these processes and ask whether integrins play a role. We perturb integrin function by a tyrosine-to-alanine substitution in membrane-proximal NPIY motif in the integrin β1 tail and show that this mutant substantially decreases microtubule nucleation and γ-tubulin accumulation at the centrosome. Because androgen stimulation promotes the interaction of the androgen receptor with Src, resulting in PI3K/AKT and MEK/ERK signaling, we asked whether these pathways are inhibited by the mutant integrin and whether they regulate microtubule nucleation. Our results indicate that the formation of the androgen receptor-Src complex and the activation of downstream pathways are significantly suppressed when cells are adhered by the mutant integrin. Inhibitor studies indicate that microtubule nucleation requires MEK/ERK but not PI3K/AKT signaling. Importantly, the expression of activated RAF-1 is sufficient to rescue microtubule nucleation inhibited by the mutant integrin by promoting the centrosomal accumulation of γ-tubulin. Our data define a novel paradigm of integrin signaling, where integrins regulate microtubule nucleation by promoting the formation of androgen receptor-Src signaling complexes to activate the MEK/ERK signaling pathway. Background: Centrosomal microtubule nucleation is important in the formation of the microtubule cytoskeleton. Results: An integrin mutant that suppresses MEK/ERK signaling substantially reduces microtubule nucleation. Expression of activated RAF-1 restores nucleation inhibited by the mutant integrin. Conclusion: Integrins promote microtubule nucleation by regulating MEK/ERK signaling. Significance: Environmental cues provided by cell-matrix adhesion contribute to the regulation of the microtubule nucleating activity of the centrosome.