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Calcium channel blockers (CCB), calcium channel antagonists or calcium antagonists are a group of medications that disrupt the movement of calcium through calcium channels. Calcium channel blockers are used as antihypertensive drugs, i.e., as medications to decrease blood pressure in patients with hypertension. CCBs are particularly effective against large vessel stiffness, one of the common causes of elevated systolic blood pressure in elderly patients. Calcium channel blockers are also frequently used to alter heart rate, to prevent peripheral and cerebral vasospasm, and to reduce chest pain caused by angina pectoris.
Charybdotoxin (ChTX) is a 37 amino acid neurotoxin from the venom of the scorpion Leiurus quinquestriatus hebraeus (deathstalker) that blocks calcium-activated potassium channels. This blockade causes hyperexcitability of the nervous system. It is a close homologue of agitoxin and both toxins come from Leiurus quinquestriatus hebraeus. It is named after Charybdis, a sea monster from Greek myth.
A conotoxin is one of a group of neurotoxic peptides isolated from the venom of the marine cone snail, genus Conus.
SK channels are a subfamily of calcium-activated potassium channels. They are so called because of their small single channel conductance in the order of 10 pS. SK channels are a type of ion channel allowing potassium cations to cross the cell membrane and are activated (opened) by an increase in the concentration of intracellular calcium through N-type calcium channels. Their activation limits the firing frequency of action potentials and is important for regulating afterhyperpolarization in the neurons of the central nervous system as well as many other types of electrically excitable cells. This is accomplished through the hyperpolarizing leak of positively charged potassium ions along their concentration gradient into the extracellular space. This hyperpolarization causes the membrane potential to become more negative. SK channels are thought to be involved in synaptic plasticity and therefore play important roles in learning and memory.
Taicatoxin (TCX) is a snake toxin that blocks voltage-dependent L-type calcium channels and small conductance Ca2+-activated K+ channels. The name taicatoxin (TAIpan + CAlcium + TOXIN) is derived from its natural source, the taipan snake, the site of its action, calcium channels, and from its function as a toxin. Taicatoxin was isolated from the venom of Australian taipan snake, Oxyuranus scutellatus scutellatus. TCX is a secreted protein, produced in the venom gland of the snake.
Calciseptine (CaS) is a natural neurotoxin isolated from the black mamba Dendroaspis p. polylepis venom. This toxin consists of 60 amino acids with four disulfide bonds. Calciseptine specifically blocks L-type calcium channels, but not other voltage-dependent Ca2+ channels such as N-type and T-type channels.
Tityustoxin is a toxin found in the venom of scorpions from the subfamily Tityinae. By binding to voltage-dependent sodium ion channels and potassium channels, they cause sialorrhea, lacrimation and rhinorrhea.
The P-type calcium channel is a type of voltage-dependent calcium channel. Similar to many other high-voltage-gated calcium channels, the α1 subunit determines most of the channel's properties. The 'P' signifies cerebellar Purkinje cells, referring to the channel's initial site of discovery. P-type calcium channels play a similar role to the N-type calcium channel in neurotransmitter release at the presynaptic terminal and in neuronal integration in many neuronal types.
N-type calcium channels also called Cav2.2 channels are voltage gated calcium channels that are localized primarily on the nerve terminals and dendrites as well as neuroendocrine cells. The calcium N-channel consists of several subunits: the primary subunit α1B and the auxiliary subunits α2δ and β. The α1B subunit forms the pore through which the calcium enters and helps to determine most of the channel's properties. These channels play an important role in the neurotransmission during development. In the adult nervous system, N-type calcium channels are critically involved in the release of neurotransmitters, and in pain pathways. N-type calcium channels are the target of ziconotide, the drug prescribed to relieve intractable cancer pain. There are many known N-type calcium channel blockers that function to inhibit channel activity, although the most notable blockers are ω-conotoxins.
Calcium channel, voltage-dependent, L type, alpha 1D subunit is a protein that in humans is encoded by the CACNA1D gene. Cav1.3 channels belong to the Cav1 family, which form L-type calcium currents and are sensitive to selective inhibition by dihydropyridines (DHP).
Potassium channel blockers are agents which interfere with conduction through potassium channels.
The voltage-dependent N-type calcium channel subunit alpha-1B is a protein that in humans is encoded by the CACNA1B gene. The α1B protein, together with β and α2δ subunits forms N-type calcium channel PMID 26386135. It is a R-type calcium channel.
Tertiapin is a 21-amino acid peptide isolated from venom of the European honey bee. It blocks two different types of potassium channels, inward rectifier potassium channels (Kir) and calcium activated large conductance potassium channels (BK).
Acid-sensing ion channels (ASICs) are neuronal voltage-insensitive sodium channels activated by extracellular protons permeable to Na+. ASIC1 also shows low Ca2+ permeability. ASIC proteins are a subfamily of the ENaC/Deg superfamily of ion channels. These genes have splice variants that encode for several isoforms that are marked by a suffix. In mammals, acid-sensing ion channels (ASIC) are encoded by five genes that produce ASIC protein subunits: ASIC1, ASIC2, ASIC3, ASIC4, and ASIC5. Three of these protein subunits assemble to form the ASIC, which can combine into both homotrimeric and heterotrimeric channels typically found in both the central nervous system and peripheral nervous system. However, the most common ASICs are ASIC1a and ASIC1a/2a and ASIC3. ASIC2b is non-functional on its own but modulates channel activity when participating in heteromultimers and ASIC4 has no known function. On a broad scale, ASICs are potential drug targets due to their involvement in pathological states such as retinal damage, seizures, and ischemic brain injury.
TROX-1 is a drug which acts as a potent blocker of the Cav2 type calcium channels. It was developed as a potential analgesic after the discovery that the selective Cav2.2 blocker ziconotide is an active analgesic with similar efficacy to strong opioid drugs. Unlike ziconotide, TROX-1 is not so selective, and also blocks the Cav2.1 and Cav2.3 calcium channel subtypes, but it has the great advantage of being orally active, whereas ziconotide must be administered intrathecally, by injection into the spinal fluid. In animal studies of TROX-1, analgesic effects were observed with similar efficacy to NSAIDs such as naproxen or diclofenac, and anti-allodynia effects equivalent to pregabalin or duloxetine.
Huwentoxins (HWTX) are a group of neurotoxic peptides found in the venom of the Chinese bird spider Haplopelma schmidti. The species was formerly known as Haplopelma huwenum, Ornithoctonus huwena and Selenocosmia huwena. While structural similarity can be found among several of these toxins, HWTX as a group possess high functional diversity.
Leconotide is an ω-conotoxin peptide isolated from the venom of Conus catus which is under investigation as an analgesic drug for the treatment of pain conditions.
The ion channel hypothesis of Alzheimer’s disease (AD), also known as the channel hypothesis or the amyloid beta ion channel hypothesis, is a more recent variant of the amyloid hypothesis of AD, which identifies amyloid beta (Aβ) as the underlying cause of neurotoxicity seen in AD. While the traditional formulation of the amyloid hypothesis pinpoints insoluble, fibrillar aggregates of Aβ as the basis of disruption of calcium ion homeostasis and subsequent apoptosis in AD, the ion channel hypothesis in 1993 introduced the possibility of an ion-channel-forming oligomer of soluble, non-fibrillar Aβ as the cytotoxic species allowing unregulated calcium influx into neurons in AD.
Protoxin-I, also known as ProTx-I, or Beta/omega-theraphotoxin-Tp1a, is a 35-amino-acid peptide neurotoxin extracted from the venom of the tarantula Thrixopelma pruriens. Protoxin-I belongs to the inhibitory cystine knot (ICK) family of peptide toxins, which have been known to potently inhibit voltage-gated ion channels. Protoxin-I selectively blocks low voltage threshold T-type calcium channels, voltage gated sodium channels and the nociceptor cation channel TRPA1. Due to its unique ability to bind to TRPA1, Protoxin-I has been implicated as a valuable pharmacological reagent with potential applications in clinical contexts with regards to pain and inflammation
Grammostola mechanotoxin #4, also known as M-theraphotoxin-Gr1a (M-TRTX-Gr1a), is a neurotoxin isolated from the venom of the spider Chilean rose tarantula Grammostola spatulate. This amphiphilic peptide, which consists of 35 amino acids, belongs to the inhibitory cysteine knot (ICK) peptide family. It reduces mechanical sensation by inhibiting mechanosensitive channels (MSCs).
References
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- 1 2 3 4 Bourinet, Emmanuel; et al. (2001). "Interaction of SNX482 with Domains III and IV Inhibits Activation Gating of α1E (CaV2.3) Calcium Channels". Biophysical Journal. Elsevier BV. 81 (1): 79–88. Bibcode:2001BpJ....81...79B. doi:10.1016/s0006-3495(01)75681-0. ISSN 0006-3495. PMC 1301493 . PMID 11423396.
- 1 2 Arroyo, G (2003-08-15). "SNX482 selectively blocks P/Q Ca2+ channels and delays the inactivation of Na+ channels of chromaffin cells". European Journal of Pharmacology. Elsevier BV. 475 (1–3): 11–18. doi:10.1016/s0014-2999(03)02084-3. ISSN 0014-2999. PMID 12954354.
- ↑ Kimm, T.; Bean, B. P. (2014-07-09). "Inhibition of A-Type Potassium Current by the Peptide Toxin SNX-482". Journal of Neuroscience. Society for Neuroscience. 34 (28): 9182–9189. doi:10.1523/jneurosci.0339-14.2014. ISSN 0270-6474. PMC 4087201 . PMID 25009251.
- ↑ Wang, Gang; et al. (1999-11-01). "An R-Type Ca2+Current in Neurohypophysial Terminals Preferentially Regulates Oxytocin Secretion". The Journal of Neuroscience. Society for Neuroscience. 19 (21): 9235–9241. doi:10.1523/jneurosci.19-21-09235.1999. ISSN 0270-6474. PMC 6782897 . PMID 10531427.
- ↑ Trevisan, Gabriela; Oliveira, Sara Marchesan (2022). "Animal Venom Peptides Cause Antinociceptive Effects by Voltage-gated Calcium Channels Activity Blockage". Current Neuropharmacology. Bentham Science Publishers Ltd. 20 (8): 1579–1599. doi:10.2174/1570159x19666210713121217. ISSN 1570-159X. PMC 9881091 . PMID 34259147.