Neurokinin A

Neurokinin A (NKA), also known as Substance K or Neurokinin α, is a neuropeptide that belongs to the tachykinin neuropeptide family. It is encoded by the TAC1 gene in humans. Neurokinin A acts primarily as a neurotransmitter and neuromodulator in the central nervous system (CNS) and the peripheral nervous system (PNS). It plays a significant role in the regulation of various physiological processes, including pain perception, vasodilation, bronchoconstriction, and modulation of the endocrine system.

Structure and Synthesis

Neurokinin A is derived from a precursor protein known as preprotachykinin-A (PPT-A), which also gives rise to another important tachykinin, Substance P. The processing of PPT-A involves a series of enzymatic steps that result in the production of Neurokinin A, among other peptides. Neurokinin A is a decapeptide, consisting of ten amino acids.

Receptors

Neurokinin A exerts its effects primarily through the activation of the neurokinin receptors, specifically the NK2 receptor. These receptors are part of the G protein-coupled receptor (GPCR) family, which initiates a cascade of intracellular events upon activation. The NK2 receptor has a high affinity for Neurokinin A and is predominantly found in the smooth muscle of various tissues, including the bronchi, gastrointestinal tract, and blood vessels.

Functions

Neurokinin A is involved in a wide range of physiological and pathological processes:

• Pain Transmission: It facilitates the transmission of pain signals in the central and peripheral nervous system.
• Cardiovascular System: Neurokinin A can induce vasodilation, leading to a decrease in blood pressure.
• Respiratory System: It can cause bronchoconstriction, making it of interest in the study of respiratory conditions such as asthma.
• Gastrointestinal System: Neurokinin A affects gastrointestinal motility and secretion, playing a role in digestive processes.

Clinical Significance

Due to its involvement in pain, inflammation, and various autonomic functions, Neurokinin A and its receptors are potential targets for the development of new therapeutic agents. Drugs that block the action of Neurokinin A (NK2 receptor antagonists) are being explored for the treatment of conditions such as asthma, irritable bowel syndrome (IBS), and certain types of pain.

Research Directions

Research on Neurokinin A continues to explore its role in disease and health, aiming to uncover new therapeutic strategies for tachykinin-related disorders. The development of selective NK2 receptor antagonists is a particularly active area of investigation.