Protein kinase inhibitor K‐252a and fusicoccin induce similar initial changes in ion transport of parsley suspension cells

Abstract

The protein kinase inhibitor K‐252a induces a rapid, transient decrease of extracellular pH and [K+], and a concomitant increase in extracellular [Ca2+] in suspensions of cultured parsley cells. These effects are subsequently reversed. As with K‐252a, fusicoccin also induces similar changes in pH and extracellular [Ca2+], but reversion does not occur. Acidification by HCI also leads to an increase in external [Ca2+], suggesting that the changes in extracellular [Ca2+] are mainly due to a pH‐dependent displacement of Ca2+ ionically bound to the cell wall. The artificial acidification by HCI is rapidly followed by cell‐mediated alkalinization, a process associated with K2 release and rebinding of Ca2+. Any change in external pH or [K+] induced by K‐252a, fusicoccin, or HCI is followed by an uptake of 45Ca2+ into cellular pools. The results show that K‐252a may be a valuable tool for studying the complex regulation of ion transport which may involve changes in the phosphorylation of unknown proteins.