Neurophysin II (NPII)

Neurophysin II is a 10-kDa carrier protein that is essential for the synthesis, transport, and storage of the hormone arginine vasopressin (AVP). Both AVP and neurophysin II are derived from a common precursor protein, prepro-vasopressin-neurophysin II, which is synthesized in the magnocellular neurons of the hypothalamus. Within the hypothalamic-neurohypophyseal system, neurophysin II binds to AVP to form a stable complex that protects the hormone from proteolytic degradation and facilitates its axonal transport to the posterior pituitary gland. Mutations in the gene encoding this protein lead to misfolding and accumulation within the endoplasmic reticulum, causing the death of vasopressinergic neurons and resulting in familial neurohypophyseal diabetes insipidus. While not a direct target for traditional pharmacological agonists or antagonists, it is a critical focus for research into protein-misfolding diseases and serves as a biomarker for neurohypophyseal function.

Other names

Vasopressin-associated neurophysinVasopressin-neurophysin 2-copeptinNeurophysin-IIAVP-NPIIPrepro-AVP

Neurophysin II functions by non-covalently binding the hormone arginine vasopressin within neurosecretory granules, ensuring its stability and correct trafficking from the site of synthesis in the hypothalamus to the site of release in the posterior pituitary.