Open AccessActivation of a serine/threonine kinase that phosphorylates microtubule‐associated protein 1B in vitro by growth factors and phorbol esters in quiescent rat fibroblastic cells
Author(s) -
HOSHI Minako,
NISHIDA Eisuke,
INAGAKI Masaki,
GOTOH Yukiko,
SAKAI Hikoichi
Publication year - 1990
Publication title -
european journal of biochemistry
Language(s) - English
Resource type - Journals
eISSN - 1432-1033
pISSN - 0014-2956
DOI - 10.1111/j.1432-1033.1990.tb19366.x
Subject(s) - casein kinase 2 , protein kinase a , cyclin dependent kinase 2 , mitogen activated protein kinase kinase , c raf , map2k7 , microbiology and biotechnology , map kinase kinase kinase , protein kinase c , mapk14 , cyclin dependent kinase 9 , kinase , cgmp dependent protein kinase , biochemistry , biology , chemistry
We have previously found and characterized a mitogen‐activated, serine/threonine‐specific protein kinase that specifically phosphorylates microtubule‐associated protein 2 (MAP2) in vitro , which we call here MAP2 kinase [Hoshi, M., Nishida, E. & Sakai, H. (1988) J. Biol. Chem. 263 , 5396–5401; Hoshi, M., Nishida, E. & Sakai, H. (1989) Eur. J. Biochem. 184 , 477–486]. In this study, we have found another serine/threonine‐specific protein kinase that is activated by various mitogens. The activated kinase utilized microtubule‐associated protein 1B (MAP1B) as the major substrate in vitro , so we tentatively call it MAP1B kinase (M1BK). M1BK was maximally activated 20–30 min after treatment of quiescent rat fibroblastic 3Y1 cells with epidermal growth factor (EGF), while MAP2 kinase was maximally activated within 5–10 min of EGF treatment. The EGF‐activated M1BK was eluted at about 0.15 M NaCl on a DEAE‐cellulose column, while the activated MAP2 kinase was eluted at about 0.1 M NaCl under the conditions used. The EGF‐activated M1BK was eluted as a single peak just after the activated MAP2 kinase on an HPLC gel‐filtration column. Histone, casein and ribosomal protein S6 were very poor substrates for the M1BK, while MAP2 and myelin basic protein were moderate substrates. The M1BK activity in cell extracts was inhibited by Ca 2+ , glycerol 2‐phosphate and Zn 2+ , and slightly enhanced by heparin. These data suggested that M1BK is distinct from previously described mitogen‐activated kinases such as MAP2 kinase, casein kinase II and S6 kinase. Pretreatment with cycloheximide or puromycin did not block the M1BK activation by EGF. Furthermore, incubation of the EGF‐activated M1BK with acid phosphatase inactivated the kinase activity. Therefore, M1BK may be activated by phosphorylation in EGF‐treated cells. In addition to EGF, 12‐ O ‐tetradecanoylphorbol 13‐acetate, platelet‐derived growth factor and insulin‐like growth factor‐I also induced the activation of M1BK in quiescent cells.