Specific proto-oncogenic tyrosine kinases of src family are enriched in cell-to-cell adherens junctions where the level of tyrosine phosphorylation is elevated.
To approach the transmembrane signaling pathway in the cell-to-cell adherens junctions (AJ), AJ-specific tyrosine phosphorylation was analyzed. When various types of rat adult tissues were pretreated with sodium orthovanadate, a potent inhibitor of tyrosine phosphatase, immunofluorescence microscopy showed that anti-phosphotyrosine polyclonal antibody specifically stained the undercoat of the cell-to-cell AJ. This indicates that the tyrosine kinase activity is elevated at the undercoat of the cell-to-cell AJ of adult tissues. To identify tyrosine kinases responsible for the high level of tyrosine phosphorylation at AJ, we have performed in vitro phosphorylation experiments with cell-to-cell AJ isolated from rat liver (Tsukita, Sh. and Sa. Tsukita. 1989. J. Cell Biol. 108:31-41) and immunoblotting analyses with specific antibodies for tyrosine kinases. As a result, three proto-oncogenic tyrosine kinases of src family, c-yes, c-src, and lyn kinases, were identified as major tyrosine kinases in the cell-to-cell AJ of hepatocytes. Furthermore, it was immunofluorescently shown that at least two of these kinases, c-yes and c-src kinases, were enriched at the cell-to-cell AJ of various types of cells including hepatocytes. Based on these findings, it is concluded that, in various types of cells, specific proto-oncogenic tyrosine kinases of src-family (c-yes and c-src) are enriched to work as signal mediators in the cell-to-cell AJ where the level of tyrosine phosphorylation is elevated.
Tsukita
S
S
National Institute for Physiological Sciences, Okazaki, Japan.
Oishi
K
K
Akiyama
T
T
Yamanashi
Y
Y
Yamamoto
T
T
Tsukita
S
S
D000367:Age Factors; D000818:Animals; D002448:Cell Adhesion; D002450:Cell Communication; D002462:Cell Membrane / Q000378:metabolism; D015180:Electrophoresis, Gel, Two-Dimensional; D005455:Fluorescent Antibody Technique; D016391:Genes, src; D008099:Liver / Q000166:cytology; D019000:Phosphotyrosine; D011505:Protein-Tyrosine Kinases / Q000378:metabolism* / Q000502:physiology*; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D051575:Proto-Oncogene Proteins c-yes; D016392:Proto-Oncogene Proteins pp60(c-src) / Q000502:physiology*; D051381:Rats; D014443:Tyrosine / Q000031:analogs & derivatives* / Q000378:metabolism; D014638:Vanadates / Q000494:pharmacology; D019061:src-Family Kinases
D011518:Proto-Oncogene Proteins; D019000:Phosphotyrosine; D014638:Vanadates; D014443:Tyrosine; D011505:Protein-Tyrosine Kinases; D051575:Proto-Oncogene Proteins c-yes; D016392:Proto-Oncogene Proteins pp60(c-src); C060902:lyn protein-tyrosine kinase; D019061:src-Family Kinases