The effect of tyrosine-specific protein phosphorylation on the assembly of adherens-type junctions.

Abstract

Adherens‐type junctions (AJs) are major subcellular targets for tyrosine specific protein phosphorylation [Volberg et al. (1991) Cell Regul., 2, 105–120]. Here we report on the apparent effect of such phosphorylation events on the assembly and integrity of AJs. We show that incubation of MDCK cells with potent inhibitors of tyrosine‐specific phosphatases (PTP), namely H2O2 and vanadate, leads to a dramatic increase in AJ‐associated phosphotyrosine which was apparent already within 2–5 min of treatment and progressed upon further incubation. Examination of H2O2 vanadate treated cells at later time points indicated that intercellular AJs rapidly deteriorated, concomitantly with a marked increase in the number and size of vinculin and actin containing focal contacts. In parallel, major changes were observed in cell structure and topology, as revealed by electron microscopy. These were manifested by rapid rounding‐up of the cells followed by reorganization of the cell monolayer. Other intercellular junctions, including desmosomes and tight junctions, visualized by staining with desmoplakin and ZO‐I antibodies, were not significantly affected. To verify that modulation of AJs was indeed related to tyrosine phosphorylation, we have carried out reciprocal experiments in which Rovs Sarcoma virus (RSV) transformed chick lens cells, expressing high levels of pp60src kinase, were treated with inhibitors of tyrosine kinases, (tyrphostins). We show that following such treatment, intercellular AJs which were deteriorated in the transformed cells, were reformed. Based on these observations, we propose that specific tyrosine phosphorylation of AJ components is involved in the downregulation of these cellular contacts.

Induction of phosphotyrosine in the gap junction protein, connexin431

“…The present results suggest that gap junctions in non-transformed cells might be targets for tyrosine kinases along with other types of cellular junctions and adhesion molecules [44][45][46][47]. The normal content of phosphotyrosine in Cx43 is clearly below the limit of detection.…”

“…Vanadate is a classical protein-tyrosine phosphatase (PTPase) ■"Corresponding author. Fax: (47) 22 93 57 67. E-mail; s.o.mikalsen@labmed.uio.no Abbreviations: GJIC, gap junctional intercellular communication; Cx43, connexin43; SHE, Syrian hamster embryo; PTPase, proteintyrosine phosphatase; Vanadate, orthovanadate; NP, PI, P2, the nonphosphorylated and the major phosphorylated forms of Cx43 A preliminary part of these data was presented at the IV European Congress of Cell Biology, Prague, Czech Republic, 26 June-1 July 1994 [49].…”

Thrombospondin-1 Induces Tyrosine Phosphorylation of Adherens Junction Proteins and Regulates an Endothelial Paracellular Pathway

“…Several nonreceptor PTKs are preferentially associated with the plasma membrane, including members of the src family (Tsukita et al, 1991;Matsuyoshi et al, 1992;Behrens et al, 1993;Hamaguchi et al, 1993). Src transformation increases tyrosine phosphorylation of cell-cell adherens junction proteins and diminishes cadherin-dependent, homophilic adhesion (Matsuyoshi et al, 1992;Volberg et al, 1992;Behrens et al, 1993;Hamaguchi et al, 1993). Interestingly, PTK inhibition with herbimycin A also protects against this loss of intercellular adhesion (Matsuyoshi et al, 1992;Hamaguchi et al, 1993).…”

“…PTPs play a crucial role in regulating protein tyrosine phosphorylation of adherens junctions (Volberg et al, 1992;Brady-Kalnay et al, 1995;Fuchs et al, 1996). Receptor PTP activity increases during contact inhibition of cultured cells in vitro (Gaits et al, 1995;Southey et al, 1995;Fuchs et al, 1996).…”

Hsp60C is required in follicle as well as germline cells during oogenesis in Drosophila melanogaster

“…4P) was uneven and disrupted. Likewise, immunostaining for tyrosine phosphorylation, an important regulatory event for formation of cell junctions (Volberg et al, 1992), showed that, while follicle cells in wild-type showed a smooth uniform phosphotyrosine staining of the inner and lateral faces (Fig. 4I), those in Hsp60C 1 /Hsp60C 1 chambers showed uneven and irregular staining with missing columnar arrangement (Fig.…”