An inward rectifier K+ current modulates in neuroblastoma cells the tyrosine phosphorylation of the pp125FAK and associated proteins: role in neuritogenesis.

The relationships between the integrin-mediated activation of inward rectifyier K+ channels (KIR), the phosphorylation of pp125FAK and the rescue of neuritogenesis were studied in 41A3 mouse neuroblastoma cells. Neuritogenesis, elicited by adhesion to FN-enriched substrata, was reversibly impaired by pretreating these cells with the tyrosine kinase inhibitor Herbimycin A. This impairment mimicked that operated by Cs+ ions, which selectively inhibited the integrin-mediated activation of KIR channels. Various phosphotyrosine containing cellular proteins underwent a marked increase upon cell adhesion to FN-coated dishes. This increase was significantly reduced by Cs+ addition. Immunoprecipitation of pp125FAK revealed that the phosphorylation of this kinase and several associated proteins was significantly and reversibly inhibited by Cs+, indicating that integrin-mediated activation of KIR channels is a limiting step upstream to the phosphorylation of pp125FAK in the commitment to neuritogenesis.