p38 mitogen-activated protein kinases are a class of

mitogen-activated protein kinase A mitogen-activated protein kinase (MAPK or MAP kinase) is a type of protein kinase that is specific to the amino acids serine and threonine (i.e., a serine/threonine-specific protein kinase). MAPKs are involved in directing cellular responses to ...

s (MAPKs) that are responsive to stress stimuli, such as

cytokines Cytokines are a broad and loose category of small proteins (~5–25 kDa) important in cell signaling. Cytokines are peptides and cannot cross the lipid bilayer of cells to enter the cytoplasm. Cytokines have been shown to be involved in autocrin ...

ultraviolet Ultraviolet (UV) is a form of electromagnetic radiation with wavelength from 10 nanometer, nm (with a corresponding frequency around 30 Hertz, PHz) to 400 nm (750 Hertz, THz), shorter than that of visible light, but longer than ...

irradiation, heat shock, and

osmotic Osmosis (, ) is the spontaneous net movement or diffusion of solvent molecules through a selectively-permeable membrane from a region of high water potential (region of lower solute concentration) to a region of low water potential (region of ...

shock, and are involved in cell differentiation,

apoptosis Apoptosis (from grc, ἀπόπτωσις, apóptōsis, 'falling off') is a form of programmed cell death that occurs in multicellular organisms. Biochemical events lead to characteristic cell changes (morphology) and death. These changes incl ...

and

autophagy Autophagy (or autophagocytosis; from the Ancient Greek , , meaning "self-devouring" and , , meaning "hollow") is the natural, conserved degradation of the cell that removes unnecessary or dysfunctional components through a lysosome-dependent re ...

. Persistent activation of the p38 MAPK pathway in muscle

satellite cells Myosatellite cells, also known as satellite cells, muscle stem cells or MuSCs, are small multipotent cells with very little cytoplasm found in mature muscle. Satellite cells are precursors to skeletal muscle cells, able to give rise to satellite ...

(muscle

stem cell In multicellular organisms, stem cells are undifferentiated or partially differentiated cells that can differentiate into various types of cells and proliferate indefinitely to produce more of the same stem cell. They are the earliest type o ...

s) due to

ageing Ageing ( BE) or aging ( AE) is the process of becoming older. The term refers mainly to humans, many other animals, and fungi, whereas for example, bacteria, perennial plants and some simple animals are potentially biologically immortal. In ...

, impairs muscle regeneration. p38 MAP Kinase (MAPK), also called RK or CSBP (Cytokinin Specific Binding Protein), is the mammalian

orthologue Sequence homology is the biological homology between DNA, RNA, or protein sequences, defined in terms of shared ancestry in the evolutionary history of life. Two segments of DNA can have shared ancestry because of three phenomena: either a spe ...

of the

yeast Yeasts are eukaryotic, single-celled microorganisms classified as members of the fungus kingdom. The first yeast originated hundreds of millions of years ago, and at least 1,500 species are currently recognized. They are estimated to constitut ...

Hog1p MAP kinase, which participates in a signaling cascade controlling cellular responses to cytokines and stress. Four p38 MAP kinases, p38-α (

MAPK14 Mitogen-activated protein kinase 14, also called p38-α, is an enzyme that in humans is encoded by the ''MAPK14'' gene. MAPK14 encodes p38α mitogen-activated protein kinase (MAPK) which is the prototypic member of the p38 MAPK family. p38 MAPKs ...

), -β (

MAPK11 Mitogen-activated protein kinase 11 is an enzyme that in humans is encoded by the ''MAPK11'' gene. Function The protein encoded by this gene is a member of the MAP kinase family. MAP kinases act as an integration point for multiple biochemical ...

), -γ ( MAPK12 / ERK6), and -δ (

MAPK13 Mitogen-activated protein kinase 13 (MAPK 13), also known as stress-activated protein kinase 4 (SAPK4), is an enzyme that in humans is encoded by the ''MAPK13'' gene. Function The protein encoded by this gene is a member of the MAP kinase fami ...

/ SAPK4), have been identified. Similar to the SAPK/JNK pathway, p38 MAP kinase is activated by a variety of cellular stresses including

shock, inflammatory cytokines,

lipopolysaccharides Lipopolysaccharides (LPS) are large molecules consisting of a lipid and a polysaccharide that are bacterial toxins. They are composed of an O-antigen, an outer core, and an inner core all joined by a covalent bond, and are found in the outer me ...

(LPS),

light, and

growth factors A growth factor is a naturally occurring substance capable of stimulating cell proliferation, wound healing, and occasionally cellular differentiation. Usually it is a secreted protein or a steroid hormone. Growth factors are important for regu ...

MKK3 Dual specificity mitogen-activated protein kinase kinase 3 is an enzyme that in humans is encoded by the ''MAP2K3'' gene. The protein encoded by this gene is a dual specificity protein kinase that belongs to the MAP kinase kinase family. This k ...

and SEK activate p38 MAP kinase by

phosphorylation In chemistry, phosphorylation is the attachment of a phosphate group to a molecule or an ion. This process and its inverse, dephosphorylation, are common in biology and could be driven by natural selection. Text was copied from this source, wh ...

at Thr-180 and Tyr-182. Activated p38 MAP kinase has been shown to phosphorylate and activate MAPKAP kinase 2 and to phosphorylate the transcription factors

ATF2 Activating transcription factor 2, also known as ATF2, is a protein that, in humans, is encoded by the ''ATF2'' gene. Function This gene encodes a transcription factor that is a member of the leucine zipper family of DNA-binding proteins. This ...

, Mac,

MEF2 In the field of molecular biology, myocyte enhancer factor-2 (Mef2) proteins are a family of transcription factors which through control of gene expression are important regulators of cellular differentiation and consequently play a critical rol ...

, and

p53 p53, also known as Tumor protein P53, cellular tumor antigen p53 (UniProt name), or transformation-related protein 53 (TRP53) is a regulatory protein that is often mutated in human cancers. The p53 proteins (originally thought to be, and often s ...

. p38 also has been shown to phosphorylate post-transcriptional regulating factors like

TTP TTP may refer to: Arts, entertainment, and media * ''Tractatus Theologico-Politicus'', a book by the philosopher Baruch Spinoza Biology * Thrombotic thrombocytopenic purpura, a blood disorder * Tristetraprolin, a protein Computing * Terrori ...

, and in fruit flies it plays a role in regulating the circadian clock.

Clinical significance

Oxidative stress is the most powerfully specific stress activating p38 MAPK. Abnormal activity (higher or lower than physiological) of p38 has been implicated in pathological stresses in several tissues, that include neuronal, bone, lung, cardiac and skeletal muscle, red blood cells, and fetal tissues. The protein product of

proto-oncogene An oncogene is a gene that has the potential to cause cancer. In tumor cells, these genes are often mutated, or expressed at high levels.

RAS can increase activity of p38, and thereby cause excessively high activity of transcription factor NF-κB. This transcription factor is normally regulated from intracellular pathways that integrate signals from the surrounding tissue and the immune system. In turn these signals coordinate between cell survival and cell death. Dysregulated NF-κB activity can activate genes that cause cancer cell survival, and can also activate genes that facilitate cancer cell metastasis to other tissues.

Inhibitors

p38 inhibitors are being sought for possible therapeutic effect on autoimmune diseases and inflammatory processes, e.g. pamapimod. Some have started clinical trials, e.g. PH-797804 for

COPD Chronic obstructive pulmonary disease (COPD) is a type of progressive lung disease characterized by long-term respiratory symptoms and airflow limitation. The main symptoms include shortness of breath and a cough, which may or may not produce mu ...

. Other p38 inhibitors include BIRB 796, VX-702, SB239063, SB202190, SB203580, SCIO 469, and BMS 582949. As of 2020, losmapimod, a p38 inhibitor, is being investigated for the treatment of

facioscapulohumeral muscular dystrophy Facioscapulohumeral muscular dystrophy (FSHD) is a type of muscular dystrophy, a group of heritable diseases that cause degeneration of muscle and progressive weakness. Per the name, FSHD tends to sequentially weaken the muscles of the face, ...

(FSHD) on the basis of p38 inhibition inhibiting the effects of

DUX4 Double homeobox, 4 also known as DUX4 is a protein which in humans is encoded by the ''DUX4'' gene. Its misexpression is the cause of facioscapulohumeral muscular dystrophy (FSHD). Gene This gene is located within a D4Z4 macrosatellite repeat a ...

References

External links

*
P38mapkPathway

p38 Signaling Pathway

MAP Kinase Resource

EC 2.7.11 Protein kinases {{2.7-enzyme-stub