Requirement of focal adhesion kinase in branching tubulogenesis.
We previously demonstrated that alpha3beta1 integrins are essential to hepatocyte growth factor (HGF)-independent branching tubulogenesis in Mardin-Darby Canine Kidney (MDCK) cells. However, the involvement of integrin downstream signaling molecules remains unclear. In the present study, we successfully isolated cell lines possessing different tubulogenic potentials from the MDCK cells; cyst clones (CA4, CA6) forming cystic structures when cultured in 0.3% type I collagen gel and mass clones (M610, M611, M612) forming aggregated masses. Cyst clones maintained cystic structure in 0.1% collagen gel, whereas mass clones spontaneously developed into tubules. Both clones exhibited various morphologies when cultured on a dish: cyst clones formed aggregated islands, while mass clones were more scattered and exhibited higher migration capacity. Among several focal adhesion machinery proteins examined, only the expression and phosphorylation level of focal adhesion kinase (FAK) in mass clones was higher than in cyst clones, while other proteins showed no obvious differences. However, overexpression of wild type FAK in CA6 cells did not facilitate branching tubule formation in 0.1% collagen gel. Targeted decrease in the expression level of FAK in M610 cells with the application of antisense cDNA resulted in a marked reduction of branching tubule formation in 0.1% collagen gel and showed a down-regulation of fibronectin assembly, which is known to promote tubulogenesis. In contrast, overexpression of wild type FAK in CA6 cells had no effect on fibronectin assembly. Taken together, our data demonstrates that FAK is required, but not sufficient for HGF-independent branching tubulogenesis in MDCK cells.
Wei
Wei-Chun
WC
Institute of Basic Medical Sciences, National Cheng Kung University Medical College, Tainan 701, Taiwan. weichun.wei@gmail.com
Kopec
Anna K
AK
Tang
Ming-Jer
MJ
D000818:Animals; D002460:Cell Line; D002465:Cell Movement / Q000502:physiology; D048430:Cell Shape; D003094:Collagen / Q000378:metabolism; D004285:Dogs; D051416:Focal Adhesion Protein-Tyrosine Kinases / Q000235:genetics / Q000378:metabolism*; D017228:Hepatocyte Growth Factor / Q000235:genetics / Q000378:metabolism; D006801:Humans; D007684:Kidney Tubules / Q000166:cytology* / Q000254:growth & development* / Q000378:metabolism
D017228:Hepatocyte Growth Factor; D003094:Collagen; D051416:Focal Adhesion Protein-Tyrosine Kinases