Kalirin Inhibition of Inducible Nitric-oxide Synthase

Abstract

Nitric oxide (NO) acts as a neurotransmitter. However, excess NO produced from neuronal NO synthase (nNOS) or inducible NOS (iNOS) during inflammation of the central nervous system can be neurotoxic, disrupting neurotransmitter and hormone production and killing neurons. A screen of a hippocampal cDNA library showed that a unique region of the iNOS protein interacts with Kalirin, previously identified as an interactor with a secretory granule peptide biosynthetic enzyme. Kalirin associates with iNOS in vitro and in vivo and inhibits iNOS activity by preventing the formation of iNOS homodimers. Expression of exogenous Kalirin in pituitary cells dramatically reduces iNOS inhibition of ACTH secretion. Thus Kalirin may play a neuroprotective role during inflammation of the central nervous system by inhibiting iNOS activity.

Reversing Synapse Loss in Alzheimer's Disease: Rho-Guanosine Triphosphatases and Insights from Other Brain Disorders

“…The functional consequences of this decrease are not clear, but, interestingly, kalirin-7 associates with inducible nitric oxide synthase (iNOS) in the hippocampus resulting in the downregulation of its enzymatic activity [76,78]. These data are in line with the findings that iNOS levels and activity are increased in AD [79,80], suggesting that the decrease of kalirin-7 in patients with AD contributes to further augment iNOS activity and exacerbate AD pathology [76].…”

Kalirin: a novel genetic risk factor for ischemic stroke

“…KALRN encodes for a guanine nucleotide exchange factor (GEF) that activates Rho proteins, and is therefore a multifunctional protein involved, among others, in neuronal morphogenesis and secretory granule maturation (Ferraro et al 2007;Rabiner et al 2005). Additionally, Kalirin may have a neuroprotective role by inhibiting inducible nitric-oxide synthase (iNOS) activity (Ratovitski et al 1999), and participates in the regulation of ischemic signal transduction (Beresewicz et al 2008).…”

Access of a Membrane Protein to Secretory Granules Is Facilitated by Phosphorylation

“…Prior to the experiment, cells were incubated in three changes of CSFM-Air over 1.5 h. Basal collections of medium were for 30 min each; these were followed by one 30-min collection in the presence of 1 mM BaCl 2 (31). Collected medium was centrifuged after addition of protease inhibitors.…”

“…The cells were then incubated on ice in ice-cold buffer (20 mM PIPES, 2 mM Na 2 EDTA, 50 mM NaF, 10 mM Na 4 P 2 O 7 and 1 mM Na 3 VO 4 , pH 7.5) with protease inhibitors (30 g/ml phenylmethylsulfonyl fluoride, 2 g/ml leupeptin, 2 g/ml pepstatin, 16 g/ml benzamidine, 5 g/ml lima bean trypsin inhibitor) and 1% Triton X-100 (500 l) added (15 min) (31). A suspension of the scraped cells was centrifuged at 250,000 ϫ g for 20 min (4°C).…”

“…Cell Extract Immunoprecipitation and Western Blot Analysis-A 100-mm dish of confluent AtT-20 PAM-1 cells was extracted as described above (31), and a suspension of the scraped cells was centrifuged at 304,000 ϫ g for 20 min (4°C). Aliquots (200 l) from the supernatant were incubated with 10 l of the exon A antibody or the P-Ser , cells were metabolically labeled, and pulse-chase experiments were performed (10,11,24,35).…”