The activity of the wheat MAP kinase phosphatase 1 is regulated by manganese and by calmodulin

Abstract

MAPK phosphatases (MKPs) are negative regulators of MAPKs in eukaryotes and play key roles in the regulation of different cellular processes. However in plants, little is known about the regulation of these Dual Specific Phosphatases (DSPs) by Ca2+ and calmodulin (CaM). Here, we showed that the wheat MKP (TMKP1) harboring a calmodulin (CaM) binding domain, binds to CaM in a Ca2+-dependent manner. In addition, TMKP1 exhibited a phosphatase activity in vitro that is specifically enhanced by Mn2+ and to a lesser extent by Mg2+, but without any synergistic effect between the two bivalent cations. Most interestingly, CaM/Ca2+ complex inhibits the catalytic activity of TMKP1 in a CaM-dose dependent manner. However, in the presence of Mn2+ this activity is enhanced by CaM/Ca2+ complex. These dual regulatory effects seem to be mediated via interaction of CaM/Ca2+ to the CaM binding domain in the C-terminal part of TMKP1. Such effects were not reported so far, and raise a possible role for CaM and Mn2+ in the regulation of plant MKPs during cellular response to external signals.