Differential regulation of MAP kinase activation by a novel splice variant of human MAP kinase phosphatase-2.
MAP kinase phosphatase-2 (MKP-2) is a member of the family of dual specificity phosphatases that functions to inactivate the ERK and JNK MAP kinase signalling pathways. Here, we identify a novel human MKP-2 variant (MKP-2-S) lacking the MAP kinase binding site but retaining the phosphatase catalytic domain. Endogenous MKP-2-S transcripts and proteins were found in PC3 prostate and MDA-MB-231 breast cancer cells and also human prostate biopsies. Cellular transfection of MKP-2-S gave rise to a nuclear protein of 33kDa which displayed phosphatase activity comparable to the formerly described long form of MKP-2 (MKP-2-L). Due to its lack of a kinase interacting motif (KIM), MKP-2-S did not bind to JNK or ERK; MKP-2-L bound ERK and to a lesser extent JNK. Protein turnover of adenoviral expressed MKP-2-S was accelerated relative to MKP-2-L, with a greater susceptibility to proteosomal-mediated degradation. MKP-2-S retained its ability to deactivate JNK in a similar manner as MKP-2-L and was an effective inhibitor of LPS-stimulated COX-2 induction. However, unlike MKP-2-L, MKP-2-S was unable to reverse serum-induced ERK activation or significantly inhibit endothelial cell proliferation. These findings reveal the occurrence of a novel splice variant of MKP-2 which is unable to bind ERK and may be significant in the dysregulation of MAP kinase activity in certain disease states, particularly in breast and prostate cancers.
Division of Physiology and Pharmacology, Strathclyde Institute of Pharmacy and Biomedical Sciences, University of Strathclyde, Glasgow, Scotland, UK.
Laurence C
LC
Cadalbert
Callum M
CM
Sloss
Margaret R
MR
Cunningham
Mashael
M
Al-Mutairi
Alan
A
McIntire
Janet
J
Shipley
Robin
R
Plevin
D000595:Amino Acid Sequence; D001665:Binding Sites; D002460:Cell Line; D054637:Dual-Specificity Phosphatases / Q000235:genetics / Q000378:metabolism*; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D048031:JNK Mitogen-Activated Protein Kinases / Q000378:metabolism; D054639:Mitogen-Activated Protein Kinase Phosphatases / Q000235:genetics / Q000378:metabolism*; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D008969:Molecular Sequence Data; D011485:Protein Binding; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism; D012326:RNA Splicing; D034741:RNA, Small Interfering / Q000378:metabolism; D015398:Signal Transduction; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism
D020033:Protein Isoforms; D034741:RNA, Small Interfering; D048049:Extracellular Signal-Regulated MAP Kinases; D048031:JNK Mitogen-Activated Protein Kinases; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D054639:Mitogen-Activated Protein Kinase Phosphatases; C490583:DUSP4 protein, human; D054637:Dual-Specificity Phosphatases