INVESTIGADORES
PODEROSO Juan Jose
congresos y reuniones científicas
Título:
A Novel Mitochondrial Nitric Oxide Synthase is Regulated during Rat Brain
Autor/es:
RIOBÓ NA; MELANI M; PODEROSO JJ
Lugar:
San Francisco, USA
Reunión:
Congreso; First International Conference Biology, Chemistry ad Therapeutic Applications of Nitric Oxide; 2000
Institución organizadora:
NO Society
Resumen:
In this study, we report the existence of a NOS variant exclusively localized in rat brain mitochondria (mtNOS). In the adult brain, both mtNOS (144 kDa) and classical 157 kDa NOS I were detected in synaptosomes with antibodies against the C-terminal domain of NOS I. However, the 144 kDa protein was present only in purified mitochondria. The 144 kDa protein Was not recognized either by antibodies against the N-terminal (1-181) region of NOS I or against the other NOS isoforms. The Km for L-arginine of the mtNOS variant was higher than that of cytosolic NOS I (12.7 uM vs 2 uM. He activity was dependent on Ca/CaM, NADPH, and BH4 and inhibited by NG-nitro-L-arginine, coincubation with an anti NOS I antibody or proteinase K treatment. Interestingly, during brain development, mtNOS and extramitochondrial NOS I showed different expression patterns. During postnatal days 0-4 (P0-P4) only mtNOS was detected in the particulate fraction while, from P6 up to adult stage, the 157 kDa isoform was co-expressed with mtNOS in synaptosomes. MtNOS was highly active at birth (151 pmol 3H-citrulline min-1 mg-1) dropping abruptly between P10-P20 and then recovering a lower activity that persisted in the adult (14 pmol 3H-citrulline min-1 mg-1). The contribution of NOS I was more significant after P10, representing about 80% of the synaptosomal activity. Thus, mtNOS appears to account for all NOS activity in the first days of life while the classical NOS I prevails in the adult stage. In addition, MnSOD activity followe a temporal pattern similar to that of mtNOS. The results suggest that brain mtNOS is an active variant of  NOS I and that it is regulated during brain development. Whether this variant is the result of alternative splicing or a post-translocational clivage of the N-terminal remains to be elucidated.