Pamlin-induced tyrosine phosphorylation of SUp62 protein in primary mesenchyme cells during early embryogenesis in the sea urchin, Hemicentrotus pulcherrimus

Ingression of primary mesenchyme cells (PMC) is associated with the encount er of basal lamina including pamlin. it was found that sea urchin embryos h ave a protein that binds antihuman local adhesion kinase (FAK) antibodies, yet it has a 62 kDa homo-dimeric structure. Thus, this protein was distinct ive from known FAK, and was named SUp62. In mesenchyme blastulae, one of th e subunits increased its apparent. molecular mass slightly but distinctivel y then restored the original molecular mass in early gastrulae. This tempor al and stage-specific shifting of the molecular mass was associated with th e occurrence of tyrosine phosphorylation of a subunit that did not increase the apparent molecular mass. Herbimycin A induced the hyperphosphorylation of tyrosine residues of SUp62, and inhibited the occurrence of molecular m ass shifting. Immunohistochemistry showed a strong positive signal of SUp62 and phosphotyrosine in PMC. Herbimycin A also severely but reversibly inhi bited PMC dissociation, migration and gastrulation. Tyrosine phosphorylatio n of SUp62 was induced when PMC were incubated with pamlin in vitro, and it was initiated within 10 min after onset of the incubation. It reached its peak in 1 h, and declined gradually in the next 1 h, indicating that pamlin -induced tyrosine phosphorylation of SUp62 occurs closely associated with a cquiring PMC migration activity.