Dystrophin-associated protein complex

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The dystrophin-associated protein complex, also known as the dystrophin-associated glycoprotein complex is a multiprotein complex that includes dystrophin and the dystrophin-associated proteins. [1] It is one of the two protein complexes that make up the costamere in striated muscle cells. The other complex is the integrin-vinculin-talin complex.

Contents

Structure

The dystrophin-associated protein complex includes dystrophin. [2] [3] Dystrophin binds to actin of the cytoskeleton, and also to proteins in the extracellular matrix. [3]

The dystrophin-associated protein complex also contains dystrophin-associated proteins. [2] This includes a four subunit sarcoglycan complex, which is fixed to dystrophin in muscle cells. [4]

In the epithelia of the kidney, dystrophin may be replaced with utrophin. [3]

Aquaporin 4 may be connected to the dystrophin-associated protein complex. [5]

Function

The dystrophin-associated protein complex is important for cell structure and cell signalling. [3] It is one of two protein complexes found in the costamere in striated muscle fibres.

Clinical significance

Many forms of muscular dystrophy are associated with disorders of the dystrophin-associated protein complex. [6]

Muscular dystrophy, the result of mutations in the genes that encode for dystrophin and the associated proteins that binds to it can arise in various forms. [7] The most common form is known as Duchenne muscular dystrophy (DMD). [8] DMD is usually discovered in early childhood and is most often seen occurring in males. There are several associated symptoms that can be observed in such patients including but not limited to a delay in walking and sitting, difficulty in breathing and heart failure. [9] [10] These symptoms are found as a result of the inability to synthesize dystrophin and associate protein complexes that leave muscles weak and unable to repair any damaged sustained. These perpetually weak muscles prohibit normal physical activity. [8]

Therapy

There has been extensive research to discover treatment for DMD. The most common drug treated against DMD is known to be Deflazacort yielding the greatest benefits with the most acceptable side effects. Physical therapy consists of varying exercises that aim to increase muscle strength and durability so to facilitate normal physical activity and is recommended to begin as early as possible after diagnosis. Contracture intervention is recommended for patients in the middle ambulatory stage. However, surgical approach to DMD is declining as less invasive treatment becomes available. While treatment for DMD has been observed to improve muscle function and quality of life, a cure to the debilitating disease remains to be found. [7] [11]

Therapeutic Microdystrophin

Related Research Articles

Muscular dystrophy Genetic disorder

Muscular dystrophies (MD) are a genetically and clinically heterogeneous group of rare neuromuscular diseases that cause progressive weakness and breakdown of skeletal muscles over time. The disorders differ as to which muscles are primarily affected, the degree of weakness, how fast they worsen, and when symptoms begin. Some types are also associated with problems in other organs.

Dystrophin Rod-shaped cytoplasmic protein

Dystrophin is a rod-shaped cytoplasmic protein, and a vital part of a protein complex that connects the cytoskeleton of a muscle fiber to the surrounding extracellular matrix through the cell membrane. This complex is variously known as the costamere or the dystrophin-associated protein complex (DAPC). Many muscle proteins, such as α-dystrobrevin, syncoilin, synemin, sarcoglycan, dystroglycan, and sarcospan, colocalize with dystrophin at the costamere. It has a molecular weight of 427 kDa

Duchenne muscular dystrophy Type of muscular dystrophy

Duchenne muscular dystrophy (DMD) is a severe type of muscular dystrophy that primarily affects boys. Muscle weakness usually begins around the age of four, and worsens quickly. Muscle loss typically occurs first in the thighs and pelvis followed by the arms. This can result in trouble standing up. Most are unable to walk by the age of 12. Affected muscles may look larger due to increased fat content. Scoliosis is also common. Some may have intellectual disability. Females with a single copy of the defective gene may show mild symptoms.

Becker muscular dystrophy Genetic muscle disorder

Becker muscular dystrophy is an X-linked recessive inherited disorder characterized by slowly progressing muscle weakness of the legs and pelvis. It is a type of dystrophinopathy. This is caused by mutations in the dystrophin gene, which encodes the protein dystrophin. Becker muscular dystrophy is related to Duchenne muscular dystrophy in that both result from a mutation in the dystrophin gene, but has a milder course.

Sarepta Therapeutics, Inc. is a medical research and drug development company with corporate offices and research facilities in Cambridge, Massachusetts, United States. Incorporated in 1980 as AntiVirals, shortly before going public the company changed its name from AntiVirals to AVI BioPharma soon with stock symbol AVII and in July 2012 changed name from AVI BioPharma to Sarepta Therapeutics and SRPT respectively. As of the end of 2019, the company has two approved drugs.

Utrophin

Utrophin is a protein that in humans is encoded by the UTRN gene.

Costamere

The costamere is a structural-functional component of striated muscle cells which connects the sarcomere of the muscle to the cell membrane.

Originally identified as Kirsten ras associated gene (krag), Sarcospan (SSPN) is a 25-kDa transmembrane protein located in the dystrophin-associated protein complex of skeletal muscle cells, where it is most abundant. It contains four transmembrane spanning helices with both N- and C-terminal domains located intracellularly. Loss of SSPN expression occurs in patients with Duchenne muscular dystrophy. Dystrophin is required for proper localization of SSPN. SSPN is also an essential regulator of Akt signaling pathways. Without SSPN, Akt signaling pathways will be hindered and muscle regeneration will not occur.

Dystrobrevin is a protein that binds to dystrophin in the costamere of skeletal muscle cells. In humans, there are at least two isoforms of dystrobrevin, dystrobrevin alpha and dystrobrevin beta.

Ataluren

Ataluren, sold under the brand name Translarna, is a medication for the treatment of Duchenne muscular dystrophy. It was designed by PTC Therapeutics.

Syntrophin, alpha 1

Alpha-1-syntrophin is a protein that in humans is encoded by the SNTA1 gene. Alpha-1 syntrophin is a signal transducing adaptor protein and serves as a scaffold for various signaling molecules. Alpha-1 syntrophin contains a PDZ domain, two Pleckstrin homology domain and a 'syntrophin unique' domain.

Integrin alpha 7

Alpha-7 integrin is a protein that in humans is encoded by the ITGA7 gene. Alpha-7 integrin is critical for modulating cell-matrix interactions. Alpha-7 integrin is highly expressed in cardiac muscle, skeletal muscle and smooth muscle cells, and localizes to Z-disc and costamere structures. Mutations in ITGA7 have been associated with congenital myopathies and noncompaction cardiomyopathy, and altered expression levels of alpha-7 integrin have been identified in various forms of muscular dystrophy.

SGCA

Alpha-sarcoglycan is a protein that in humans is encoded by the SGCA gene.

In molecular biology, exon skipping is a form of RNA splicing used to cause cells to “skip” over faulty or misaligned sections (exons) of genetic code, leading to a truncated but still functional protein despite the genetic mutation.

mir-31

miR-31 has been characterised as a tumour suppressor miRNA, with its levels varying in breast cancer cells according to the metastatic state of the tumour. From its typical abundance in healthy tissue is a moderate decrease in non-metastatic breast cancer cell lines, and levels are almost completely absent in mouse and human metastatic breast cancer cell lines. Mir-31-5p has also been observed upregulated in Zinc Deficient rats compared to normal in ESCC and in other types of cancers when using this animal model. There has also been observed a strong encapsulation of tumour cells expressing miR-31, as well as a reduced cell survival rate. miR-31's antimetastatic effects therefore make it a potential therapeutic target for breast cancer. However, these two papers were formally retracted by the authors in 2015.

Drisapersen is an experimental drug that was under development by BioMarin, after acquisition of Prosensa, for the treatment of Duchenne muscular dystrophy. The drug is a 2'-O-methyl phosphorothioate oligonucleotide that alters the splicing of the dystrophin RNA transcript, eliminating exon 51 from the mature dystrophin mRNA.

Eteplirsen

Eteplirsen is a medication to treat, but not cure, some types of Duchenne muscular dystrophy (DMD), caused by a specific mutation. Eteplirsen only targets specific mutations and can be used to treat about 14% of DMD cases. Eteplirsen is a form of antisense therapy.

Ezutromid

Ezutromid is an orally administered small molecule utrophin modulator currently involved in a Phase 2 clinical trial produced by Summit Therapeutics for the treatment of Duchenne muscular dystrophy (DMD). DMD is a fatal x-linked recessive disease affecting approximately 1 in 5000 males and is a designated orphan disease by the FDA and European Medicines Agency. Approximately 1/3 of the children obtain DMD as a result of spontaneous mutation in the dystrophin gene and have no family history of the disease. Dystrophin is a vital component of mature muscle function, and therefore DMD patients have multifarious forms of defunct or deficient dystrophin proteins that all manifest symptomatically as muscle necrosis and eventually organ failure. Ezutromid is theorized to maintain utrophin, a protein functionally and structurally similar to dystrophin that precedes and is replaced by dystrophin during development. Utrophin and dystrophin are reciprocally expressed, and are found in different locations in a mature muscle cell. However, in dystrophin-deficient patients, utrophin was found to be upregulated and is theorized to replace dystrophin in order to maintain muscle fibers. Ezutromid is projected to have the potential to treat all patients suffering with DMD as it maintains the production of utrophin to counteract the lack of dystrophin to retard muscle degeneration. Both the FDA and European Medicines Agency has given ezutromid an orphan drug designation. The FDA Office of Orphan Products and Development offers an Orphan Drug Designation program (ODD) that allows drugs aimed to treat diseases that affect less than 200,000 people in the U.S. monetary incentives such as a period of market exclusivity, tax incentives, and expedited approval processes.

Golodirsen, sold under the brand name Vyondys 53, is a medication used for the treatment of Duchenne muscular dystrophy (DMD) in people who have a confirmed mutation of the dystrophin gene that is amenable to exon 53 skipping. It is an antisense oligonucleotide drug of phosphorodiamidate morpholino oligomer (PMO) chemistry.

Viltolarsen, sold under the brand name Viltepso, is a medication used for the treatment of Duchenne muscular dystrophy (DMD). Viltolarsen is a Morpholino antisense oligonucleotide.

References

  1. Charvet B, Ruggiero F, Le Guellec D (April 2012). "The development of the myotendinous junction. A review". Muscles, Ligaments and Tendons Journal. 2 (2): 53–63. PMC   3666507 . PMID   23738275.
  2. 1 2 Dystrophin-Associated+Protein+Complex at the US National Library of Medicine Medical Subject Headings (MeSH)
  3. 1 2 3 4 Welling PA (2008-01-01). "Scaffolding Proteins in Transport Regulation". In Alpern RJ, Herbert SC (eds.). CHAPTER 12 - Scaffolding Proteins in Transport Regulation. Seldin and Giebisch's The Kidney (Fourth Edition). San Diego: Academic Press. pp. 325–341. doi:10.1016/b978-012088488-9.50015-2. ISBN   978-0-12-088488-9.
  4. Kirschner J, Lochmüller H (2011-01-01). Griggs RC, Amato AA (eds.). "Sarcoglycanopathies". Handbook of Clinical Neurology. Muscular Dystrophies. Elsevier. 101: 41–46. doi:10.1016/b978-0-08-045031-5.00003-7. ISBN   9780080450315. PMID   21496623.
  5. Binder DK (2017-01-01). "Water Homeostasis Dysfunction in Epilepsy". In Badaut J, Plesnila N (eds.). Chapter 17 - Water Homeostasis Dysfunction in Epilepsy. Brain Edema. San Diego: Academic Press. pp. 315–335. doi:10.1016/b978-0-12-803196-4.00017-5. ISBN   978-0-12-803196-4.
  6. Ehmsen J, Poon E, Davies K (July 2002). "The dystrophin-associated protein complex". Journal of Cell Science. 115 (Pt 14): 2801–2803. doi:10.1242/jcs.115.14.2801. PMID   12082140.
  7. 1 2 Lovering RM, Porter NC, Bloch RJ (December 2005). "The muscular dystrophies: from genes to therapies". Physical Therapy. 85 (12): 1372–1388. doi:10.1093/ptj/85.12.1372. PMC   4496952 . PMID   16305275.
  8. 1 2 Passamano L, Taglia A, Palladino A, Viggiano E, D'Ambrosio P, Scutifero M, et al. (October 2012). "Improvement of survival in Duchenne Muscular Dystrophy: retrospective analysis of 835 patients". Acta Myologica. 31 (2): 121–125. PMC   3476854 . PMID   23097603.
  9. Gao QQ, McNally EM (July 2015). "The Dystrophin Complex: Structure, Function, and Implications for Therapy". Comprehensive Physiology. 5 (3): 1223–1239. doi:10.1002/cphy.c140048. ISBN   9780470650714. PMC   4767260 . PMID   26140716.
  10. Ryder S, Leadley RM, Armstrong N, Westwood M, de Kock S, Butt T, et al. (April 2017). "The burden, epidemiology, costs and treatment for Duchenne muscular dystrophy: an evidence review". Orphanet Journal of Rare Diseases. 12 (1): 79. doi:10.1186/s13023-017-0631-3. PMC   5405509 . PMID   28446219.
  11. Wagner KR, Lechtzin N, Judge DP (February 2007). "Current treatment of adult Duchenne muscular dystrophy". Biochimica et Biophysica Acta (BBA) - Molecular Basis of Disease. The Muscular Dystrophies: Molecular Basis and Therapeutic Strategies. 1772 (2): 229–237. doi:10.1016/j.bbadis.2006.06.009. PMID   16887341.
  12. https://www.chugai-pharm.co.jp/english/news/detail/20211216150001_885.html
  13. https://investorrelations.sarepta.com/static-files/ba326dff-2918-46bd-9a42-4ba73676a77f
  14. "Delandistrogene moxeparvovec - Roche/Sarepta Therapeutics - AdisInsight". adisinsight.springer.com.