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A Biochemical Analysis Beyond the Muscle Contraction and Its Relation with Isaac Syndrome Valdemir Aquino De Freitas Neto*

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A Biochemical Analysis Beyond the Muscle Contraction and Its Relation with Isaac Syndrome Valdemir Aquino De Freitas Neto* ISSN: 2643-4571 Neto et al. Int J Rare Dis Disord 2020, 3:028 DOI: 10.23937/2643-4571/1710028 Volume 3 | Issue 2 International Journal of Open Access Rare Diseases & Disorders REVIEW ARTICLE A Biochemical Analysis beyond the Muscle Contraction and its Relation with Isaac Syndrome Valdemir Aquino de Freitas Neto* Colégio GGE, Brazil Check for updates *Corresponding author: Valdemir Aquino de Freitas Neto, Colégio GGE, Jaboatão dos Guararapes, Pernambuco, Brazil inside the cell induces the Na+ channel to close eventu- Abstract ally, the K+ channels to open and, then, the K+ ions flow Isaac Syndrome is an autoimmune disease related to the in- from inside to outside the cell membrane, causing the voluntary contraction of skeletal muscles. The author, thus, is going to connect it with the process of muscle contraction repolarization of sarcolemma [1]. Through the action through a biochemical study, analysing the pathway from potential process, the impulse is able to follow the signal a nervous impulse to the open of voltage-gated Potassium to a motor neuron, consuming energy since the ATPase channels and the releasing of Ca2+ on myofibrils. This paper hydrolyses the ATP into ADP + Pi, releasing energy to intends to introduce this rare disease and to induce further + + researches in order to find a cure. restore the concentration of Na and K against the con- centration gradient by active transport. Also, in muscle Keywords cells, that action potential is called end-plate potential. Isaac Syndrome, Muscle contraction, Nervous impulse, Ca2+, Voltage-gated Potassium channels That process can go wrong if the nervous impulse ac- tivates the pump with no order of the brain and this is Abbreviations the main point around Isaac Syndrome or Neuromyoto- Na+: Sodium Cation; K+: Potassium Cation; ATP: Adenosine nia. This type of error is important to comprehend pos- Triphosphate; ADP: Adenosine Diphosphate; P: Inorganic i sible causes to Neuromyotonia and to start researchers Phosphate; Ca2+: Calcium Cation; Mg2+: Magnesium Cation; Cd2+: Cadmium Cation; TnC: Troponin C; TnT: Troponin T; in order to find out how to prevent the involuntary con- TnI: Troponin I; VGKC: Voltage-Gate Potassium Channels; traction of skeletal muscle in rare diseases. CASPR2: Contactin-Associated Protein like 2 The author explored, through a biochemical way, over 22 recent data based on researches that involve Introduction the whole process of muscle contraction; the main The muscle contraction process starts on the Na+/ works are presented in the references section and they K+ pump during a nervous impulse. A nervous impulse were extracted from the most known biochemical and comes from the nervous system and goes to a motor biophysical journals in order to develop a critical and neuron through the action potential. The action poten- substantiate review, meeting the majority criteria on tial consists in wave of positive charges that induces the the biochemical method. + + open of the voltage-gated Na channels, the Na ions, Results on the Muscle Contraction Process which stay in high concentration outside the cellular membrane, flow through passive diffusion from outside When the impulse reaches the motor neuron, it 2+ 2+ to inside the cell, following the concentration gradi- opens the Ca channels and the Ca ions flow to inside 2+ ent and the depolarization of the sarcolemma, the cell the motor neuron cell. The entry of Ca into the cell, membrane of muscle cells, causes the slightly positive induces the mobilization of Acetylcholine vesicles, by charge inside the cell. In that way, the positive charge docking, to the cell membrane and the vesicles fusion, Citation: Neto VAF (2020) A Biochemical Analysis beyond the Muscle Contraction and its Relation with Isaac Syndrome. Int J Rare Dis Disord 3:028. doi.org/10.23937/2643-4571/1710028 Accepted: December 29, 2020; Published: December 31, 2020 Copyright: © 2020 Neto VAF, et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Neto et al. Int J Rare Dis Disord 2020, 3:028 • Page 1 of 4 • DOI: 10.23937/2643-4571/1710028 ISSN: 2643-4571 releasing the Acetylcholine to the gap junctional in a tains a Tropomyosin-binding site and an Actin-capping process called Synapsis [2]. site, when the TnI-TnC rearrangement occurs, shifts the Tropomyosin from the closed state to the open state There are many receptors of Acetylcholine, called (azimuthal positions) and, at this state, the Tropomy- Nicotinic Acetylcholine receptors due its affinity with osin uncovers the Actin-Myosin binding site and, also, nicotine. In this way, when the Acetylcholine is released support it; because of that behaviour, some scientists to muscle cells, it binds with cholinergic receptors that call the Tropomyosin an allosteric switch. There are a activate the ryanodine receptors, which are Ca2+ chan- few diseases related to mutations in the β-Tropomyo- nels, and the Ca2+ ions are released by the sarcoplasmic sin gene, called TPM2, and the most severe affect the reticulum, a modified endoplasmic reticulum which can heart contractions, like Hypertrophic Cardiomyopathy; afford the amount of Ca2+ ions to the muscle cell [3]. a good way of treatment is the use of beta-blockers as Therefore, the Ca2+ ions are released to the myofibrils. medication that inhibit the abnormal activity of the Tro- The myofibrils are a huge complex of proteins which pomyosin in heart. contain the Troponin complex, Tropomyosin, Actin fil- aments and Myosin. The Myosin is a motor protein, what means that it plays a binding role with Actin when an input of ATP is The Troponin is a protein complex with the Tropo- hydrolyzed. The Myosin has several parts as Troponin myosin that lies between Actin filaments. The Troponin and it is, basically, divided in head, neck and tail. The complex is made of Troponin C, Troponin T, and Tropo- Myosin tail has a carboxyl-terminal group (-COOH) in or- nin I [4]. The Troponin C has this name because it pos- der to make the dimerization of heavy amino acids res- sess 4 structural EF-Hands, which are 2 two α-helices idues because of its α-helicoidal coiled-coil form and to interrelated through a loop with negative charge ions practice the cargo binding [13], that is, to carry through and its configuration allows EF-Hands to bind to bivalent cell transportation amino acids capable of binding along ions, like Ca2+, Mg2+ and Cd2+ [5]. The Troponin I have 3 the Actin filament [14]. The Myosin neck is responsible different isoforms: The slow skeletal muscle, the fast for the light chains, which belongs to the EF-Hands fam- skeletal muscle and the cardiac; in general, the Tropo- ily and the most important is the Calmodulin, because nin I works as a structural support for Troponin C, when 2+ the association of Myosin light chains is fundamental the site TnI-TnC binds to Ca , there is a rearrangement for the congregation of macromolecular complexes since the 2 EF-Hands move closer, what orientates the that work as motor protein, like dynein and kinesin. The helices, resulting in the opening of a hydrophobic path Myosin head has an amine-terminal group (-NH2) and that allows the switch peptide of Troponin I to act, and, it is responsible for binding to the Actin-Myosin sites, consequently, the Troponin complex is able to interact which lies on Actin filaments, via N terminal [15]. The with Actin and Tropomyosin [6]. The Troponin T devel- hydrolysis of ATP in Myosin head occurs when there is ops a hard-structural role because the C terminal do- an increase of Ca2+ by the sarcoplasmic reticulum and main makes the fixation of the Troponin complex to the Calmodulin is able to phosphorylate Myosin light the Actin filament, while the N terminal and the linking chains at the serine and threonine residues [16]. Thus, terminal stabilizes the interaction with Tropomyosin [7] the repetition of that phosphorylation promotes the (Figure 1). activity of ATPase, hydrolysing ATP into ADP + iP and, The Tropomyosin normally blocks the Myosin II, the consequently, releasing enough amount of energy to most known Myosin, binding sites in order to prevent a the contraction of Myosin head toward the Actin-My- muscle contraction without a nerve input and without osin binding site. When the Myosin head reaches the wasting ATP with no purpose [8,9]. The Tropomyosin is Actin-Myosin binding site, if and only if the Tropomy- associated with those 3 Troponin parts (TnC, TnT, and osin is on the open state, a cross-bridge is formed; so, TnI) [10]. In a high concentration of Ca2+, the N terminal the Myosin head releases the Pi, causing a conforma- [11] Actinsites of TnT, called Leiomodin [12], which con- tional change in the Myosin structure that increases the affinity between Actin and Myosin (this process is called power stroke). In that scope, there are hundreds of Myosin heads interacting with only one Actin filament, so they move it relatively fast, causing the muscle contraction by the repetition of the cycle. Discussion That all said, the Isaac Syndrome, which is called Neu- romyotonia, is a hyperexcitability of motor nerves that causes overly muscular activity. In fact, motor nerves are different from motor neuron because the second Figure 1: Structure of Troponin. one communicates directly with the muscular cells Neto et al. Int J Rare Dis Disord 2020, 3:028 • Page 2 of 4 • DOI: 10.23937/2643-4571/1710028 ISSN: 2643-4571 while the first one sends signals from the Central Ner- traction process in order to obtain a high understanding vous System to the Peripherical Nervous System.
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