DYNAMICS OF CONNEXIN43 PHOSPHORYLATION IN PP60(V-SRC)-TRANSFORMED CELLS

Connexin43 phosphorylation was analysed in non-transformed and pp60v-s rc-transformed Rat-I fibroblasts. Connexin43 appeared to be the primar y connexin expressed in these cells. Although gap-junctional communica tion was disrupted in pp60v-src-transformed cells, they contained more connexin43 protein and RNA than their non-transformed counterpart. Co nnexin43 was phosphorylated within minutes of its synthesis in both ce ll types and appeared to be degraded while in the phosphorylated state . Phosphopeptide and phosphoamino acid analyses suggested that connexi n43 in both cell types contained at least five fragments with serine p hosphorylation. The major difference in connexin43 phosphorylation bet ween the pp60v-src-transformed and non-transformed cells was that, whe reas approx. 70 % of the phosphorylated connexin43 in the former conta ined phosphotyrosine, this phosphoamino acid was not detected in conne xin43 isolated from the latter cells. These data support the hypothesi s that phosphorylation of connexin43 on tyrosine is critical for the b lockade of gap-junctional communication which occurs concomitantly wit h transformation by the pp60v-src onco-gene.