Integration of protein kinases mTOR and extracellular signal-regulated kinase 5 in regulating nucleocytoplasmic localization of NFATc4.
The target of rapamycin (TOR) signaling regulates the nucleocytoplasmic shuttling of transcription factors in yeast. Whether the mammalian counterpart of TOR (mTOR) also regulates nucleocytoplasmic shuttling is not known. Using a phospho-specific monoclonal antibody, we demonstrate that mTOR phosphorylates Ser(168,170) of endogenous NFATc4, which are conserved gate-keeping Ser residues that control NFAT subcellular distribution. The mTOR acts as a basal kinase during the resting state to maintain NFATc4 in the cytosol. Inactivation and nuclear export of NFATc4 are mediated by rephosphorylation of Ser(168,170), which can be a nuclear event. Kinetic analyses demonstrate that rephosphorylation of Ser(168,170) of endogenous NFATc4 is mediated by mTOR and, surprisingly, by extracellular signal-regulated kinase 5 (ERK5) mitogen-activated protein kinase as well. Ablation of ERK5 in the Erk5(-/-) cells ascertains defects in NFATc4 rephosphorylation and nucleocytoplasmic shuttling. In addition, phosphorylation of NFATc4 by ERK5 primes subsequent phosphorylation mediated by CK1alpha. These results demonstrate that distinct protein kinases are integrated to phosphorylate the gate-keeping residues Ser(168,170) of NFATc4, to regulate subcellular distribution. These data also expand the repertoire of physiological substrates of mTOR and ERK5.
Yang
Teddy T C
TT
Department of Molecular Pharmacology, Albert Einstein College of Medicine, 1300 Morris Park Ave., Bronx, NY 10461, USA.
Yu
Raymond Y L
RY
Agadir
Anissa
A
Gao
Guo-Jian
GJ
Campos-Gonzalez
Roberto
R
Tournier
Cathy
C
Chow
Chi-Wing
CW
D021581:Active Transport, Cell Nucleus; D000818:Animals; D000911:Antibodies, Monoclonal; D000918:Antibody Specificity; D019556:COS Cells; D002460:Cell Line; D002478:Cells, Cultured; D002522:Chlorocebus aethiops; D006224:Cricetinae; D051379:Mice; D018345:Mice, Knockout; D048054:Mitogen-Activated Protein Kinase 7 / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D008954:Models, Biological; D050778:NFATC Transcription Factors / Q000737:chemistry / Q000172:deficiency / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D010766:Phosphorylation; D011494:Protein Kinases / Q000378:metabolism*; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D012694:Serine / Q000737:chemistry; D058570:TOR Serine-Threonine Kinases; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism
D000911:Antibodies, Monoclonal; D050778:NFATC Transcription Factors; C467907:Nfatc4 protein, mouse; D011994:Recombinant Proteins; D012694:Serine; D011494:Protein Kinases; C546843:mTOR protein, mouse; D058570:TOR Serine-Threonine Kinases; D048054:Mitogen-Activated Protein Kinase 7; D048051:p38 Mitogen-Activated Protein Kinases