Tyrosine Phosphorylation of the β 4 Integrin Cytoplasmic Domain Mediates Shc Signaling to Extracellular Signal-regulated Kinase and Antagonizes Formation of Hemidesmosomes *

阅读量：

作者：

M Dans，Laurent Gagnoux-Palacios，P Blaikie，S Klein，A Mariotti，FG Giancotti

展开

摘要：

Ligation of the αβintegrin induces tyrosine phosphorylation of the βcytoplasmic domain, followed by recruitment of the adaptor protein Shc and activation of mitogen-activated protein kinase cascades. We have used Far Western analysis and phosphopeptide competition assays to map the sites in the cytoplasmic domain of βthat are required for interaction with Shc. Our results indicate that, upon phosphorylation, Tyr, or secondarily Tyr, interacts with the SH2 domain of Shc, whereas Tyr, or secondarily Tyr, interacts with its phosphotyrosine binding (PTB) domain. An inactivating mutation in the PTB domain of Shc, but not one in its SH2 domain, suppresses the activation of Shc by αβ. In addition, mutation of βTyr, which binds to the PTB domain of Shc, but not of Tyrand Tyr, which interact with its SH2 domain, abolishes the activation of ERK by αβ. Phenylalanine substitution of the βtyrosines able to interact with the SH2 or PTB domain of Shc does not affect incorporation of αβin the hemidesmosomes of 804G cells. Exposure to the tyrosine phosphatase inhibitor orthovanadate increases tyrosine phosphorylation of β4 and disrupts the hemidesmosomes of 804G cells expressing recombinant wild type β. This treatment, however, exerts a decreasing degree of inhibition on the hemidesmosomes of cells expressing versions of βcontaining phenylalanine substitutions at Tyrand Tyr, at Tyrand Tyr, or at all four tyrosine phosphorylation sites. These results suggest that βTyrinteracts in a phosphorylation-dependent manner with the PTB domain of Shc. This event is required for subsequent tyrosine phosphorylation of Shc and signaling to ERK but not formation of hemidesmosomes.

展开

关键词：

Humans Cell Line Desmosomes Cytoplasm Vanadates Phenylalanine Tyrosine Phosphotyrosine Phosphopeptides Recombinant Proteins