Calcineurin (CaN) is a calcium and calmodulin dependent serine/threonine protein phosphatase (also known as protein phosphatase 3, and calcium-dependent serine-threonine phosphatase). [2] It activates the T cells of the immune system and can be blocked by drugs. Calcineurin activates nuclear factor of activated T cell cytoplasmic (NFATc), a transcription factor, by dephosphorylating it. The activated NFATc is then translocated into the nucleus, where it upregulates the expression of interleukin 2 (IL-2), which, in turn, stimulates the growth and differentiation of the T cell response. Calcineurin is the target of a class of drugs called calcineurin inhibitors, which include ciclosporin, voclosporin, pimecrolimus and tacrolimus.
Calcineurin is a heterodimer of a 61-kD calmodulin-binding catalytic subunit, calcineurin A and a 19-kD Ca2+-binding regulatory subunit, calcineurin B. There are three isozymes of the catalytic subunit, each encoded by a separate gene (PPP3CA, PPP3CB, and PPP3CC) and two isoforms of the regulatory, also encoded by separate genes (PPP3R1, PPP3R2).
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When an antigen-presenting cell interacts with a T cell receptor on T cells, there is an increase in the cytoplasmic level of calcium, which activates calcineurin by binding a regulatory subunit and activating calmodulin binding. [3] Calcineurin induces transcription factors (NFATs) that are important in the transcription of IL-2 genes. IL-2 activates T-helper lymphocytes and induces the production of other cytokines. In this way, it governs the action of cytotoxic lymphocytes. The amount of IL-2 being produced by the T-helper cells is believed to influence the extent of the immune response significantly.
Calcineurin inhibitors are prescribed for adult rheumatoid arthritis (RA) as a single drug or in combination with methotrexate. The microemulsion formulation is approved by the U.S. Food and Drug Administration for treatment of severely active RA. It is also prescribed for: psoriatic arthritis, psoriasis, acute ocular Behçet's disease, juvenile idiopathic arthritis, adult and juvenile polymyositis and dermatomyositis, adult and juvenile systemic lupus erythematosus, adult lupus membranous nephritis, systemic sclerosis, aplastic anemia, steroid-resistant nephrotic syndrome, atopic dermatitis, severe corticosteroid-dependent asthma, severe ulcerative colitis, pemphigus vulgaris, myasthenia gravis, and dry eye disease, with or without Sjögren's syndrome (administered as ophthalmic emulsion). [4]
Calcineurin is linked to receptors for several brain chemicals including glutamate, dopamine and GABA. [5] An experiment with genetically-altered mice that could not produce calcineurin showed similar symptoms as in humans with schizophrenia: impairment in working memory, attention deficits, aberrant social behavior, and several other abnormalities characteristic of schizophrenia. [6]
Calcineurin along with NFAT, may improve the function of diabetics' pancreatic beta cells. [7] [8] Thus tacrolimus contributes to the frequent development of new diabetes following renal transplantation. [9]
Calcineurin/NFAT signaling is required for perinatal lung maturation and function. [10]
Calcineurin inhibitors such as tacrolimus are used to suppress the immune system in organ allotransplant recipients to prevent rejection of the transplanted tissue. [11]
Calcineurin has been shown to interact with RCAN1 [12] and AKAP5. [13]
Immunosuppressive drugs, also known as immunosuppressive agents, immunosuppressants and antirejection medications, are drugs that inhibit or prevent the activity of the immune system.
The T-cell receptor (TCR) is a protein complex found on the surface of T cells, or T lymphocytes, that is responsible for recognizing fragments of antigen as peptides bound to major histocompatibility complex (MHC) molecules. The binding between TCR and antigen peptides is of relatively low affinity and is degenerate: that is, many TCRs recognize the same antigen peptide and many antigen peptides are recognized by the same TCR.
Stuart L. Schreiber is a scientist at Harvard University and co-founder of the Broad Institute. He has been active in chemical biology, especially the use of small molecules as probes of biology and medicine. Small molecules are the molecules of life most associated with dynamic information flow; these work in concert with the macromolecules that are the basis for inherited information flow.
The FKBPs, or FK506 binding proteins, constitute a family of proteins that have prolyl isomerase activity and are related to the cyclophilins in function, though not in amino acid sequence. FKBPs have been identified in many eukaryotes, ranging from yeast to humans, and function as protein folding chaperones for proteins containing proline residues. Along with cyclophilin, FKBPs belong to the immunophilin family.
Nuclear factor of activated T-cells (NFAT) is a family of transcription factors shown to be important in immune response. One or more members of the NFAT family is expressed in most cells of the immune system. NFAT is also involved in the development of cardiac, skeletal muscle, and nervous systems. NFAT was first discovered as an activator for the transcription of IL-2 in T cells but has since been found to play an important role in regulating many more body systems. NFAT transcription factors are involved in many normal body processes as well as in development of several diseases, such as inflammatory bowel diseases and several types of cancer. NFAT is also being investigated as a drug target for several different disorders.
Serine/threonine-protein phosphatase 2A catalytic subunit alpha isoform is an enzyme that is encoded by the PPP2CA gene.
Nuclear factor of activated T-cells, cytoplasmic 2 is a protein that in humans is encoded by the NFATC2 gene.
Serine/threonine-protein phosphatase 2A 55 kDa regulatory subunit B alpha isoform is an enzyme regulator that in humans is encoded by the PPP2R2A gene.
Myosin light-chain phosphatase, also called myosin phosphatase (EC 3.1.3.53; systematic name [myosin-light-chain]-phosphate phosphohydrolase), is an enzyme (specifically a serine/threonine-specific protein phosphatase) that dephosphorylates the regulatory light chain of myosin II:
A-kinase anchor protein 5 is a protein that in humans is encoded by the AKAP5 gene.
Nuclear factor of activated T-cells, cytoplasmic 3 is a protein that in humans is encoded by the NFATC3 gene.
Nuclear factor of activated T-cells, cytoplasmic 4 is a protein that in humans is encoded by the NFATC4 gene.
Serine/threonine-protein phosphatase 2B catalytic subunit beta isoform (PP2BB) is an enzyme that in humans is encoded by the PPP3CB gene.
Calcineurin subunit B type 1 also known as protein phosphatase 2B regulatory subunit 1 is a protein that in humans is encoded by the PPP3R1 gene.
Calcineurin-binding protein cabin-1 is a protein that in humans is encoded by the CABIN1 gene.
Serine/threonine-protein phosphatase 2B catalytic subunit gamma isoform (PP2BC) is an enzyme that in humans is encoded by the PPP3CC gene.
Calcineurin subunit B type 2 is a protein that in humans is encoded by the PPP3R2 gene. Among its related pathways are MAPK signaling pathway and GPCR pathway. GO annotations related to this gene include calcium ion binding. An important paralog of this gene is CHP1.
Serine/threonine-protein phosphatase 2B catalytic subunit alpha isoform (PP2BA) is a protein that in humans is encoded by the PPP3CA gene.
Protein phosphatase 2 (PP2), also known as PP2A, is an enzyme that in humans is encoded by the PPP2CA gene. The PP2A heterotrimeric protein phosphatase is ubiquitously expressed, accounting for a large fraction of phosphatase activity in eukaryotic cells. Its serine/threonine phosphatase activity has a broad substrate specificity and diverse cellular functions. Among the targets of PP2A are proteins of oncogenic signaling cascades, such as Raf, MEK, and AKT, where PP2A may act as a tumor suppressor.
Patrick G. Hogan is a cellular and molecular biologist who studies how cellular signaling leads to gene expression. He obtained his bachelor’s degree from Harvard University and a PhD in neurobiology from Harvard Medical School. In 2010, he moved to the La Jolla Institute for Immunology in San Diego as a Professor in the Division of Signaling and Gene Expression. He is a Founder and Member of the Scientific Advisory Board, CalciMedica Inc, La Jolla, CA.