mitogen-activated protein kinase 8 | |||||||
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Identifiers | |||||||
Symbol | MAPK8 | ||||||
Alt. symbols | JNK1, PRKM8 | ||||||
NCBI gene | 5599 | ||||||
HGNC | 6881 | ||||||
OMIM | 601158 | ||||||
RefSeq | NM_002750 | ||||||
UniProt | P45983 | ||||||
Other data | |||||||
Locus | Chr. 10 q11.2 | ||||||
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mitogen-activated protein kinase 9 | |||||||
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Identifiers | |||||||
Symbol | MAPK9 | ||||||
Alt. symbols | JNK2, PRKM9 | ||||||
NCBI gene | 5601 | ||||||
HGNC | 6886 | ||||||
OMIM | 602896 | ||||||
RefSeq | NM_002752 | ||||||
UniProt | P45984 | ||||||
Other data | |||||||
Locus | Chr. 5 q35 | ||||||
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mitogen-activated protein kinase 10 | |||||||
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Identifiers | |||||||
Symbol | MAPK10 | ||||||
Alt. symbols | JNK3, PRKM10 | ||||||
NCBI gene | 5602 | ||||||
HGNC | 6872 | ||||||
OMIM | 602897 | ||||||
RefSeq | NM_002753 | ||||||
UniProt | P53779 | ||||||
Other data | |||||||
Locus | Chr. 4 q22-q23 | ||||||
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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 kinase kinases, MKK4 and MKK7, and JNK can be inactivated by Ser/Thr and Tyr protein phosphatases. [1] It has been suggested that this signaling pathway contributes to inflammatory responses in mammals and insects. [ citation needed ]
The c-Jun N-terminal kinases consist of ten isoforms derived from three genes: JNK1 (four isoforms), JNK2 (four isoforms) and JNK3 (two isoforms). [2] 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. [1]
c-Jun N-terminal kinase isoforms have the following tissue distribution:
Inflammatory signals, changes in levels of reactive oxygen species, ultraviolet radiation, protein synthesis inhibitors, and a variety of stress stimuli can activate JNK. One way this activation may occur is through disruption of the conformation of sensitive protein phosphatase enzymes; specific phosphatases normally inhibit the activity of JNK itself and the activity of proteins linked to JNK activation. [4]
JNKs can associate with scaffold proteins JNK interacting proteins (JIP) as well as their upstream kinases JNKK1 and JNKK2 following their activation.
JNK, by phosphorylation, modifies the activity of numerous proteins that reside at the mitochondria or act in the nucleus. Downstream molecules that are activated by JNK include c-Jun, ATF2, ELK1, SMAD4, p53 and HSF1. The downstream molecules that are inhibited by JNK activation include NFAT4, NFATC1 and STAT3. By activating and inhibiting other small molecules in this way, JNK activity regulates several important cellular functions including cell growth, differentiation, survival and apoptosis.
JNK1 is involved in apoptosis, neurodegeneration, cell differentiation and proliferation, inflammatory conditions and cytokine production mediated by AP-1 (activation protein 1) such as RANTES, IL-8 and GM-CSF. [5]
Recently, JNK1 has been found to regulate Jun protein turnover by phosphorylation and activation of the ubiquitin ligase Itch.
Neurotrophin binding to p75NTR activates a JNK signaling pathway causing apoptosis of developing neurons. JNK, through a series of intermediates, activates p53 and p53 activates Bax which initiates apoptosis. TrkA can prevent p75NTR-mediated JNK pathway apoptosis. [6] JNK can directly phosphorylate Bim-EL, a splicing isoform of Bcl-2 interacting mediator of cell death (Bim), which activates Bim-EL apoptotic activity. JNK activation is required for apoptosis but c-jun, a protein involved in the JNK pathway, is not always required. [7]
The packaging of eukaryotic DNA into chromatin presents a barrier to all DNA-based processes that require recruitment of enzymes to their sites of action. To allow repair of double-strand breaks in DNA, the chromatin must be remodeled. [8] Chromatin relaxation occurs rapidly at the site of a DNA damage. [9] In one of the earliest steps, JNK phosphorylates SIRT6 on serine 10 in response to double-strand breaks (DSBs) or other DNA damage, and this step is required for efficient repair of DSBs. [10] Phosphorylation of SIRT6 on S10 facilitates the mobilization of SIRT6 to DNA damage sites, where SIRT6 then recruits and mono-phosphorylates poly (ADP-ribose) polymerase 1 (PARP1) at DNA break sites. [10] Half maximum accumulation of PARP1 occurs within 1.6 seconds after the damage occurs. [11] The chromatin remodeler Alc1 quickly attaches to the product of PARP1 action, a poly-ADP ribose chain, [9] allowing half of the maximum chromatin relaxation, presumably due to action of Alc1, by 10 seconds. [9] This allows recruitment of the DNA repair enzyme MRE11, to initiate DNA repair, within 13 seconds. [11]
Removal of UV-induced DNA photoproducts, during transcription coupled nucleotide excision repair (TC-NER), depends on JNK phosphorylation of DGCR8 on serine 153. [12] While DGCR8 is usually known to function in microRNA biogenesis, the microRNA-generating activity of DGCR8 is not required for DGCR8-dependent removal of UV-induced photoproducts. [12] Nucleotide excision repair is also needed for repair of oxidative DNA damage due to hydrogen peroxide (H2O2), and DGCR8 depleted cells are sensitive to H2O2. [12]
In Drosophila , flies with mutations that augment JNK signaling accumulate less oxidative damage and live dramatically longer than wild-type flies. [13] [14]
In the tiny roundworm Caenorhabditis elegans , loss-of-function mutants of JNK-1 have a decreased life span, while amplified expression of wild-type JNK-1 extends life span by 40%. [15] Worms with overexpressed JNK-1 also have significantly increased resistance to oxidative stress and other stresses. [15]
DNA repair is a collection of processes by which a cell identifies and corrects damage to the DNA molecules that encode its genome. In human cells, both normal metabolic activities and environmental factors such as radiation can cause DNA damage, resulting in tens of thousands of individual molecular lesions per cell per day. Many of these lesions cause structural damage to the DNA molecule and can alter or eliminate the cell's ability to transcribe the gene that the affected DNA encodes. Other lesions induce potentially harmful mutations in the cell's genome, which affect the survival of its daughter cells after it undergoes mitosis. As a consequence, the DNA repair process is constantly active as it responds to damage in the DNA structure. When normal repair processes fail, and when cellular apoptosis does not occur, irreparable DNA damage may occur. This can eventually lead to malignant tumors, or cancer as per the two-hit hypothesis.
A mitogen-activated protein kinase is a type of protein kinase that is specific to the amino acids serine and threonine. MAPKs are involved in directing cellular responses to a diverse array of stimuli, such as mitogens, osmotic stress, heat shock and proinflammatory cytokines. They regulate cell functions including proliferation, gene expression, differentiation, mitosis, cell survival, and apoptosis.
Protein kinase B (PKB), also known as Akt, is the collective name of a set of three serine/threonine-specific protein kinases that play key roles in multiple cellular processes such as glucose metabolism, apoptosis, cell proliferation, transcription, and cell migration.
The MAPK/ERK pathway is a chain of proteins in the cell that communicates a signal from a receptor on the surface of the cell to the DNA in the nucleus of the cell.
Casein kinase 2 (CK2/CSNK2) is a serine/threonine-selective protein kinase that has been implicated in cell cycle control, DNA repair, regulation of the circadian rhythm, and other cellular processes. De-regulation of CK2 has been linked to tumorigenesis as a potential protection mechanism for mutated cells. Proper CK2 function is necessary for survival of cells as no knockout models have been successfully generated.
Mitogen-activated protein kinase 9 is an enzyme that in humans is encoded by the MAPK9 gene.
Transcription factor Jun is a protein that in humans is encoded by the JUN gene. c-Jun, in combination with protein c-Fos, forms the AP-1 early response transcription factor. It was first identified as the Fos-binding protein p39 and only later rediscovered as the product of the JUN gene. c-jun was the first oncogenic transcription factor discovered. The proto-oncogene c-Jun is the cellular homolog of the viral oncoprotein v-jun. The viral homolog v-jun was discovered in avian sarcoma virus 17 and was named for ju-nana, the Japanese word for 17. The human JUN encodes a protein that is highly similar to the viral protein, which interacts directly with specific target DNA sequences to regulate gene expression. This gene is intronless and is mapped to 1p32-p31, a chromosomal region involved in both translocations and deletions in human malignancies.
Apoptosis signal-regulating kinase 1 (ASK1) also known as mitogen-activated protein kinase 5 (MAP3K5) is a member of MAP kinase family and as such a part of mitogen-activated protein kinase pathway. It activates c-Jun N-terminal kinase (JNK) and p38 mitogen-activated protein kinases in a Raf-independent fashion in response to an array of stresses such as oxidative stress, endoplasmic reticulum stress and calcium influx. ASK1 has been found to be involved in cancer, diabetes, rheumatoid arthritis, cardiovascular and neurodegenerative diseases.
Mitogen-activated protein kinase 14, also called p38-α, is an enzyme that in humans is encoded by the MAPK14 gene.
Mitogen-activated protein kinase 8 is a ubiquitous enzyme that in humans is encoded by the MAPK8 gene.
Dual specificity mitogen-activated protein kinase kinase 1 is an enzyme that in humans is encoded by the MAP2K1 gene.
Promyelocytic leukemia protein (PML) is the protein product of the PML gene. PML protein is a tumor suppressor protein required for the assembly of a number of nuclear structures, called PML-nuclear bodies, which form amongst the chromatin of the cell nucleus. These nuclear bodies are present in mammalian nuclei, at about 1 to 30 per cell nucleus. PML-NBs are known to have a number of regulatory cellular functions, including involvement in programmed cell death, genome stability, antiviral effects and controlling cell division. PML mutation or loss, and the subsequent dysregulation of these processes, has been implicated in a variety of cancers.
Checkpoint kinase 1, commonly referred to as Chk1, is a serine/threonine-specific protein kinase that, in humans, is encoded by the CHEK1 gene. Chk1 coordinates the DNA damage response (DDR) and cell cycle checkpoint response. Activation of Chk1 results in the initiation of cell cycle checkpoints, cell cycle arrest, DNA repair and cell death to prevent damaged cells from progressing through the cell cycle.
Dual-specificity mitogen-activated protein kinase kinase 4 is an enzyme that in humans is encoded by the MAP2K4 gene.
Dual specificity mitogen-activated protein kinase kinase 7, also known as MAP kinase kinase 7 or MKK7, is an enzyme that in humans is encoded by the MAP2K7 gene. This protein is a member of the mitogen-activated protein kinase kinase family. The MKK7 protein exists as six different isoforms with three possible N-termini and two possible C-termini.
Mitogen-activated protein kinase kinase kinase 4 is an enzyme that in humans is encoded by the MAP3K4 gene.
Protein phosphorylation is a reversible post-translational modification of proteins in which an amino acid residue is phosphorylated by a protein kinase by the addition of a covalently bound phosphate group. Phosphorylation alters the structural conformation of a protein, causing it to become activated, deactivated, or otherwise modifying its function. Approximately 13,000 human proteins have sites that are phosphorylated.
Mitogen-activated protein kinase 10 also known as c-Jun N-terminal kinase 3 (JNK3) is an enzyme that in humans is encoded by the MAPK10 gene.
The Akt signaling pathway or PI3K-Akt signaling pathway is a signal transduction pathway that promotes survival and growth in response to extracellular signals. Key proteins involved are PI3K and Akt.
DNA damage is an alteration in the chemical structure of DNA, such as a break in a strand of DNA, a nucleobase missing from the backbone of DNA, or a chemically changed base such as 8-OHdG. DNA damage can occur naturally or via environmental factors, but is distinctly different from mutation, although both are types of error in DNA. DNA damage is an abnormal chemical structure in DNA, while a mutation is a change in the sequence of base pairs. DNA damages cause changes in the structure of the genetic material and prevents the replication mechanism from functioning and performing properly. The DNA damage response (DDR) is a complex signal transduction pathway which recognizes when DNA is damaged and initiates the cellular response to the damage.
The protein products of jnk1 and jnk2 are believed to be expressed in every cell and tissue type, whereas the JNK3 protein is found primarily in brain and to a lesser extent in heart and testis