. "FUNCTION: Serine/threonine kinase which acts as an essential component of the MAP kinase signal transduction pathway. MAPK1/ERK2 and MAPK3/ERK1 are the 2 MAPKs which play an important role in the MAPK/ERK cascade. They participate also in a signaling cascade initiated by activated KIT and KITLG/SCF. Depending on the cellular context, the MAPK/ERK cascade mediates diverse biological functions such as cell growth, adhesion, survival and differentiation through the regulation of transcription, translation, cytoskeletal rearrangements. The the MAPK/ERK cascade plays also a role in initiation and regulation of meiosis, mitosis, and postmitotic functions in differentiated cells by phosphorylating a number of transcription factors. About 160 substrates have already been discovered for ERKs. Many of these substrates are localized in the nucleus, and seem to participate in the regulation of transcription upon stimulation. However, other substrates are found in the cytosol as well as in other cellular organelles, and those are responsible for processes such as translation, mitosis and apoptosis. Moreover, the MAPK/ERK cascade is also involved in the regulation of the endosomal dynamics, including lysosome processing and endosome cycling through the perinuclear recycling compartment (PNRC); as well as in the fragmentation of the Golgi apparatus during mitosis. The substrates include transcription factors (such as ATF2, BCL6, ELK1, ERF, FOS, HSF4 or SPZ1), cytoskeletal elements (such as CANX, CTTN, GJA1, MAP2, MAPT, PXN, SORBS3 or STMN1), regulators of apoptosis (such as BAD, BTG2, CASP9, DAPK1, IER3, MCL1 or PPARG), regulators of translation (such as EIF4EBP1) and a variety of other signaling-related molecules (like ARHGEF2, FRS2 or GRB10). Protein kinases (such as RAF1, RPS6KA1/RSK1, RPS6KA3/RSK2, RPS6KA2/RSK3, RPS6KA6/RSK4, SYK, MKNK1/MNK1, MKNK2/MNK2, RPS6KA5/MSK1, RPS6KA4/MSK2, MAPKAPK3 or MAPKAPK5) and phosphatases (such as DUSP1, DUSP4, DUSP6 or DUSP16) are other substrates which enable the propagation the MAPK/ERK signal to additionnal cytosolic and nuclear targets, thereby extending the specificity of the cascade. CATALYTIC ACTIVITY: ATP + a protein = ADP + a phosphoprotein. COFACTOR: Magnesium (By similarity). ENZYME REGULATION: Phosphorylated by MAP2K1/MEK1 and MAP2K2/MEK2 on Thr-202 and Tyr-204 in response to external stimuli like insulin or NGF. Both phosphorylations are required for activity. This phosphorylation causes dramatic conformational changes, which enable full activation and interaction of MAPK1/ERK2 with its substrates. Dephospphorylated and inactivated by DUSP3, DUSP6 and DUSP9. SUBUNIT: Binds both upstream activators and downstream substrates in multimolecular complexes. Found in a complex with at least BRAF, HRAS1, MAP2K1/MEK1, MAPK3 and RGS14 (By similarity). Binds to HIV-1 Nef through its SH3 domain. This interaction inhibits its tyrosine-kinase activity. Interacts with ADAM15, ARRB2, CANX, DAPK1 (via death domain), HSF4, IER3, MAP2K1/MEK1, MORG1, NISCH, and SGK1. Interacts with PEA15 and MKNK2 (By similarity). MKNK2 isoform 1 binding prevents from dephosphorylation and inactivation (By similarity). SUBCELLULAR LOCATION: Cytoplasm. Nucleus. Note=Autophosphorylation at Thr-207 promotes nuclear localization. ALTERNATIVE PRODUCTS: Event=Alternative splicing; Named isoforms=3; Name=1; IsoId=P27361-1; Sequence=Displayed; Name=2; IsoId=P27361-2; Sequence=VSP_041906; Name=3; Synonyms=ERK1b; IsoId=P27361-3; Sequence=VSP_041907; DOMAIN: The TXY motif contains the threonine and tyrosine residues whose phosphorylation activates the MAP kinases. PTM: Phosphorylated upon KIT and FLT3 signaling (By similarity). Dually phosphorylated on Thr-202 and Tyr-204, which activates the enzyme. Ligand-activated ALK induces tyrosine phosphorylation. Dephosphorylated by PTPRJ at Tyr-204. SIMILARITY: Belongs to the protein kinase superfamily. CMGC Ser/Thr protein kinase family. MAP kinase subfamily. SIMILARITY: Contains 1 protein kinase domain. GENE SYNONYMS:MAPK3 ERK1 PRKM3. COPYRIGHT: Protein annotation is derived from the UniProt Consortium (http://www.uniprot.org/). Distributed under the Creative Commons Attribution-NoDerivs License."^^ . "SEQUENCE 379 AA; 43136 MW; E6020CE413EC41F7 CRC64;"^^ . . . . . . . . . . "MK03_HUMAN"^^ . "2.7.11.24"^^ . "MAPK3"^^ . "Microtubule-associated protein 2 kinase"^^ . "MAP kinase isoform p44"^^ . "MAPK 3"^^ . "Insulin-stimulated MAP2 kinase"^^ . "ERT2"^^ . "p44-MAPK"^^ . "MAP kinase 3"^^ . "p44-ERK1"^^ . "Extracellular signal-regulated kinase 1"^^ . "ERK-1"^^ . . . . . . . . "MAAAAAQGGGGGEPRRTEGVGPGVPGEVEMVKGQPFDVGPRYTQLQYIGEGAYGMVSSAYDHVRKTRVAIKKISPFEHQTYCQRTLREIQILLRFRHENVIGIRDILRASTLEAMRDVYIVQDLMETDLYKLLKSQQLSNDHICYFLYQILRGLKYIHSANVLHRDLKPSNLLINTTCDLKICDFGLARIADPEHDHTGFLTEYVATRWYRAPEIMLNSKGYTKSIDIWSVGCILAEMLSNRPIFPGKHYLDQLNHILGILGSPSQEDLNCIINMKARNYLQSLPSKTKVAWAKLFPKSDSKALDLLDRMLTFNPNKRITVEEALAHPYLEQYYDPTDEPVAEEPFTFAMELDDLPKERLKELIFQETARFQPGVLEAP"^^ . "Mitogen-activated protein kinase 3"^^ .