TI - Activation of TrkA tyrosine kinase in embryonal carcinoma cells promotes cell compaction , independently of tyrosine phosphorylation of catenins . AB - Cadherins are transmembrane receptors whose extracellular domain mediates homophilic cell - cell interactions , while their cytoplasmic domain associates with a family of proteins known as catenins . Although the mechanisms that regulate the assembly and functional state of cadherin-catenin complexes are poorly understood , current evidence supports a role for protein tyrosine kinase activity in regulating cell adhesion and migration . Tyrosine phosphorylation of catenins is thought to mediate loss of intercellular adhesion promoted by activation of receptor tyrosine kinases in epithelial cells . Here , we show that activation of ectopically expressed TrkA , the tyrosine kinase receptor for nerve growth factor ( NGF ) , stimulates embryonal carcinoma P19 cells to develop extensive intercellular contacts and to assemble into closely packed clusters . Thus , activation of receptor tyrosine kinases can differentially regulate adhesiveness by cell-type-specific mechanisms . Furthermore , activation of TrkA in P19 and epithelial MDCK cells induces tyrosine phosphorylation of p120 ( ctn ) and of beta-catenin , irrespective of the elicited cellular response . The selective Src tyrosine kinase inhibitor PP2 , however , suppresses NGF - or HGF -induced tyrosine phosphorylation of catenins in both P19 and MDCK cells without interfering with the acquisition of a compacted or scattered phenotype . These findings provide a cogent argument for considering that tyrosine phosphorylation of catenins is dispensable for their interaction with cadherins and , ultimately , for the modulation of cadherin-based cell adhesion by receptor tyrosine kinases .