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. [5] [6]
MAP3K5 gene coding for the protein is located on chromosome 6 at locus 6q22.33. [7] and the transcribed protein contains 1,374 amino acids with 11 kinase subdomains.[ citation needed ] Northern blot analysis shows that MAP3K5 transcript is abundant in human heart and pancreas. [8]
Under nonstress conditions ASK1 is oligomerized (a requirement for its activation) through its C-terminal coiled-coil domain (CCC), but remains in an inactive form by the suppressive effect of reduced thioredoxin (Trx) and calcium and integrin binding protein 1 (CIB1). [9] Trx inhibits ASK1 kinase activity by direct binding to its N-terminal coiled-coil domain (NCC). Trx and CIB1 regulate ASK1 activation in a redox- or calcium- sensitive manner, respectively. Both appear to compete with TNF-α receptor-associated factor 2 (TRAF2), an ASK1 activator. TRAF2 and TRAF6 are then recruited to ASK1 to form a larger molecular mass complex. [10] Subsequently, ASK1 forms homo-oligomeric interactions not only through the CCC, but also the NCC, which leads to full activation of ASK1 through autophosphorylation at threonine 845. [11]
ASK1 gene transcription can be induced by inflammatory cytokines such as IL-1 and TNF-α through the activation of the NF-kb protein RelA. [6] Interestingly, TNF-α is also able to stabilize the ASK1 protein through deubiquitination. [12] Thus, unlike other members of the mitogen-activated protein kinase family, the regulation of ASK1 expression is transcriptional as well as post-transcriptional. [6]
ASK1 has been shown to interact with:
A mitogen-activated protein kinase is a type of serine/threonine-specific protein kinases 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.
Mitogen Activated Protein (MAP) kinase kinase kinase is a serine/threonine-specific protein kinase which acts upon MAP kinase kinase. Subsequently, MAP kinase kinase activates MAP kinase. Several types of MAPKKK can exist but are mainly characterized by the MAP kinases they activate. MAPKKKs are stimulated by a large range of stimuli, primarily environmental and intracellular stressors. MAPKKK is responsible for various cell functions such as cell proliferation, cell differentiation, and apoptosis. The duration and intensity of signals determine which pathway ensues. Additionally, the use of protein scaffolds helps to place the MAPKKK in close proximity with its substrate to allow for a reaction. Lastly, because MAPKKK is involved in a series of several pathways, it has been used as a therapeutic target for cancer, amyloidosis, and neurodegenerative diseases. In humans, there are at least 19 genes which encode MAP kinase kinase kinases:
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.
TRAF6 is a TRAF human protein.
TNF receptor-associated factor 2 is a protein that in humans is encoded by the TRAF2 gene.
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.
Mitogen-activated protein kinase kinase kinase 7 (MAP3K7), also known as TAK1, is an enzyme that in humans is encoded by the MAP3K7 gene.
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 6 also known as MAP kinase kinase 6 or MAPK/ERK kinase 6 is an enzyme that in humans is encoded by the MAP2K6 gene, on chromosome 17.
TNF receptor-associated factor 5 is a protein that in humans is encoded by the TRAF5 gene.
Mitogen-activated protein kinase kinase kinase 1 (MAP3K1) is a signal transduction enzyme that in humans is encoded by the autosomal MAP3K1 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.
C-jun-amino-terminal kinase-interacting protein 3 is an enzyme that in humans is encoded by the MAPK8IP3 gene.
Mitogen-activated protein kinase 12 is an enzyme that in humans is encoded by the MAP3K12 gene.
Mitogen-activated protein kinase kinase kinase kinase 2 is an enzyme that in humans is encoded by the MAP4K2 gene.
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.
Mitogen-activated protein kinase kinase kinase 6 is a protein that in humans is encoded by the MAP3K6 gene.