Nitric oxide synthase-interacting protein (NOSIP)

Nitric oxide synthase-interacting protein (NOSIP) is a multifunctional protein that acts as a key modulator of both endothelial nitric oxide synthase (eNOS) and neuronal nitric oxide synthase (nNOS) activity[1][3]. NOSIP binds the carboxyl-terminal region of the eNOS oxygenase domain, sequestering eNOS from plasma membrane caveolae, thus inhibiting nitric oxide (NO) production. It also modulates the availability and subcellular distribution of nNOS in neurons, with effects on neuronal activity–dependent NO signaling. NOSIP acts as an E3 ubiquitin ligase (RING-type), enabling protein-protein interactions and regulatory ubiquitination, and undergoes dynamic nucleocytoplasmic shuttling—being predominantly nuclear under basal conditions and exported to the cytoplasm during the G2 phase of the cell cycle[1]. NOSIP’s biological relevance is highlighted in pathophysiological contexts, including gastrointestinal diseases like Hirschsprung’s disease, where altered NOSIP expression may affect intestinal NO-mediated homeostasis, and in granulopoiesis, where decreased NOSIP levels correlate with increased NO production via nNOS during neutrophil differentiation[1][3]. Overall, it functions as a regulatory hub for nitric oxide synthase activity, with further roles in protein ubiquitination and potential disease associations.

Other names

CGI-25E3 ubiquitin-protein ligase NOSIPRING-type E3 ubiquitin transferase NOSIPeNOS-interacting protein