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Vasoactive Peptides intermediate

Alpha-Calcitonin Gene-Related Peptide

Alpha-CGRP is a potent vasodilatory neuropeptide implicated in migraine pathophysiology and neurogenic inflammation through CLR/RAMP1 receptor signaling.

By Encyclopeptide Editorial | 2 min read
cgrp vasodilation migraine calcitonin neuropeptide

Overview

Alpha-calcitonin gene-related peptide (alpha-CGRP) is a 37-amino-acid neuropeptide with potent vasodilatory and sensory neuromodulatory properties. Identified in 1982 by Amara and colleagues through molecular cloning of calcitonin gene transcripts, alpha-CGRP is the predominant CGRP isoform in sensory neurons and trigeminal ganglia. Its sequence includes a conserved C-terminal amidated residue essential for receptor binding and biological activity.

Gene Expression and Alternative Splicing

Alpha-CGRP is encoded by the CALCA gene located on chromosome 11p15.2 in humans. This single gene produces both calcitonin and alpha-CGRP through tissue-specific alternative RNA processing. In thyroid C-cells, calcitonin mRNA predominates, whereas sensory neurons preferentially express the CGRP isoform. The resulting 125-amino-acid precursor undergoes cleavage by prohormone convertase 2 and 3 to generate the mature 37-amino-acid peptide.

Receptor Complex

Alpha-CGRP signals through a heteromeric receptor complex comprising the calcitonin-like receptor (CLR) and receptor activity-modifying protein 1 (RAMP1). This CLR/RAMP1 complex couples to Gs proteins, activating adenylyl cyclase and elevating intracellular cAMP. The binding affinity of alpha-CGRP for this complex is approximately 1 nM, establishing it as the primary endogenous agonist. Amylin binds CLR with RAMP2 or RAMP3 but not RAMP1, conferring selectivity.

Cardiovascular Effects

Alpha-CGRP produces profound vasodilation in coronary, cerebral, and peripheral arteries through endothelium-independent mechanisms. The vasodilatory response involves both nitric oxide-dependent and -independent pathways. Alpha-CGRP is released from perivascular sensory nerves during tissue injury, triggering neurogenic inflammation characterized by vasodilation, plasma extravasation, and mast cell degranulation.

Role in Migraine Pathogenesis

Alpha-CGRP is elevated approximately threefold during migraine attacks compared to baseline. The trigeminovascular system, rich in CGRP-containing sensory fibers innervating meningeal blood vessels, represents the anatomical substrate for CGRP-mediated migraine. CGRP antagonists and monoclonal antibodies targeting CGRP or its receptor have revolutionized migraine treatment, offering preventive strategies with superior tolerability profiles.

Therapeutic Applications

Calcitonin gene-related peptide receptor antagonists (gepants) and monoclonal antibodies (erenumab, fremanezumab, galcanezumab) have demonstrated efficacy in both acute migraine treatment and prevention. These agents represent paradigm-shifting therapies for episodic and chronic migraine.

References

  1. Amara, S.G., et al. (1982). Alternative RNA processing. Science, 218(4577), 1122-1124.
  2. Russell, F.A., et al. (2014). Calcitonin gene-related peptide. Pharmacological Reviews, 66(1), 1-29.
  3. Edvinsson, L., et al. (2018). Calcitonin gene-related peptide in migraine and cluster headache. Neurology, 91(11), 1009-1017.

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