What is Neurokinin A?
NKA belongs to the tachykinin family, a group of signalling peptides involved in communication between nerves, smooth muscle and immune-related tissues.
NKA is a decapeptide, meaning it contains ten amino acids. Its structure includes a C-terminal amide group, a feature shared by many tachykinins and important for receptor activity.
The peptide is produced from the TAC1 gene, also known as the preprotachykinin A gene. This is one of the most important points when understanding NKA: it is closely related to substance P because both can be produced from the same gene-derived precursor.
One genetic source, different signalling roles
You can think of TAC1 as a master construction plan. Through alternative processing and splicing, the cell can produce related peptide messengers from that plan.
Depending on the precursor form and tissue, TAC1-derived products can include:
- Substance P
- Neurokinin A
- Related tachykinins such as neuropeptide K and neuropeptide gamma
The peptides may share an origin, but they are not interchangeable. They have different receptor preferences and can produce different biological effects.
The key point: NKA and substance P are family members with a shared molecular background, not identical signals.
NKA and the NK2 receptor
The NK2 receptor, short for neurokinin-2 receptor, is a cell-surface receptor in the tachykinin receptor family. It belongs to a broader class called G protein-coupled receptors, or GPCRs. GPCRs work like cellular doorbells: when the right messenger binds, they trigger a chain of internal signals.
NKA is considered the preferential natural ligand for NK2. In plain English, NKA is one of the most effective tachykinin “keys” for this receptor.
NK2 receptors are found in tissues that contain smooth muscle, including:
- The airways
- The gastrointestinal tract
- Other visceral tissues
- Selected regions of the nervous system
When NKA activates NK2 receptors, the downstream response often involves smooth muscle contraction. This is why researchers focus on the NKA–NK2 axis when studying airway narrowing and intestinal movement.
The receptor is the switch. NKA is one of the signals that flips it.
