JNK

mitogen-activated protein kinase 8
Identifiers
Symbol	MAPK8
Alt. symbols	JNK1, PRKM8
Entrez	5599
HUGO	6881
OMIM	601158
RefSeq	NM_002750
UniProt	P45983
Other data
Locus	Chr. 10 q11.2

mitogen-activated protein kinase 9
Identifiers
Symbol	MAPK9
Alt. symbols	JNK2, PRKM9
Entrez	5601
HUGO	6886
OMIM	602896
RefSeq	NM_002752
UniProt	P45984
Other data
Locus	Chr. 5 q35

mitogen-activated protein kinase 10
Identifiers
Symbol	MAPK10
Alt. symbols	JNK3, PRKM10
Entrez	5602
HUGO	6872
OMIM	602897
RefSeq	NM_002753
UniProt	P53779

c-Jun N-terminal kinases (JNKs), were originally identified as kinases that bind and phosphorylate c-Jun on Ser-63 and Ser-73 within its transcriptional activation domain. They belong to the mitogen-activated protein kinase family, and are responsive to stress stimuli, such as cytokines, ultraviolet irradiation, heat shock, and osmotic shock. They also play a role in T cell differentiation and the cellular apoptosis pathway. Activation occurs through a dual phosphorylation of threonine (Thr) and tyrosine (Tyr) residues within a Thr-Pro-Tyr motif located in kinase subdomain VIII. Activation is carried out by two MAP kinases, MKK4 and MKK7 and JNK can be inactivated by Ser/Thr and Tyr protein phosphatases. It has been suggested that this signaling pathway contributes to inflammatory responses in mammals and insects.

The c-Jun N-terminal kinases consist of ten isoforms derived from three genes: JNK1 (four isoforms), JNK2 (four isoforms) and JNK3 (two isoforms). Each gene is expressed as either 46 kDa or 55 kDa protein kinases, depending upon how the 3' coding region of the corresponding mRNA is processed. There have been no functional differences documented between the 46 kDa and the 55 kDa isoform, however, a second form of alternative splicing occurs within transcripts of JNK1 and JNK2, yielding JNK1-α, JNK2-α and JNK1-β and JNK2-β. Differences in interactions with protein substrates arise because of the mutually exclusive utilization of two exons within the kinase domain.

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