Abstract
The brain renin-angiotensin system profoundly affects the cardiovascular system, often with pathological consequences. However, many unresolved questions about its functionality remain. Recently it was shown that a novel, non-AT1, non-AT2 binding site for angiotensin II (Ang II) exists in the mammalian brain. This protein has been identified as the metalloendopeptidase neurolysin (E.C.3.4.24.16). To assess the localization of this binding site in mouse brain, 3 mice deficient in neurolysin as well as 3 wild-type mouse brains were evaluated for radioligand binding with 125I-Sarcosine1,Isoleucine8 Ang II (250 pM) in the presence of receptor-saturating concentrations of losartan (an AT1 receptor antagonist), PD123319 (an AT2 receptor antagonist ) and 150 μM parachloromercuribenzoate (to unmask the binding site) using in vitro autoradiography. Specific (10 μM Ang II displaceable) 125I-Sarcosine1,Isoleucine8 Ang II binding in wild-type mouse brains was abundant, with highest levels in the molecular layer of the cerebellum, cerebral cortex, hippocampus, amygdala, caudate-putamen, hypothalamus, lateral septum, and external plexiform layer of the olfactory bulb. There was a profound reduction in specific 125I-Sar1,Ile8 Ang II binding in neurolysin-deficient mouse brains, however, the extent of reduction was region-specific. The greatest decreases were seen in the cerebral cortex, substantia nigra, hippocampus, paraventricular thalamus, lateral septum, and nucleus accumbens in neurolysin deficient mouse brains. The cerebellar cortex and hypothalamus showed the smallest reductions in 125I-SI Ang II binding. These results verify that the previously-reported novel non-AT1, non-AT2 receptor binding protein, is neurolysin, ut that there may be additional non-AT1 non-AT2 binding sites in the mouse brain. Supported by NHLBI HL-096357.
Faculty Sponsors
Dr. Robert Speth
Project Type
Event
Location
Alvin Sherman Library
Start Date
4-13-2012 1:00 PM
End Date
4-13-2012 5:30 PM
Loss of 125I-Sarcosine1, Isoleucine8 Angiotensin II Binding in the Brain of Neurolysin Knock-Out Mice
Alvin Sherman Library
The brain renin-angiotensin system profoundly affects the cardiovascular system, often with pathological consequences. However, many unresolved questions about its functionality remain. Recently it was shown that a novel, non-AT1, non-AT2 binding site for angiotensin II (Ang II) exists in the mammalian brain. This protein has been identified as the metalloendopeptidase neurolysin (E.C.3.4.24.16). To assess the localization of this binding site in mouse brain, 3 mice deficient in neurolysin as well as 3 wild-type mouse brains were evaluated for radioligand binding with 125I-Sarcosine1,Isoleucine8 Ang II (250 pM) in the presence of receptor-saturating concentrations of losartan (an AT1 receptor antagonist), PD123319 (an AT2 receptor antagonist ) and 150 μM parachloromercuribenzoate (to unmask the binding site) using in vitro autoradiography. Specific (10 μM Ang II displaceable) 125I-Sarcosine1,Isoleucine8 Ang II binding in wild-type mouse brains was abundant, with highest levels in the molecular layer of the cerebellum, cerebral cortex, hippocampus, amygdala, caudate-putamen, hypothalamus, lateral septum, and external plexiform layer of the olfactory bulb. There was a profound reduction in specific 125I-Sar1,Ile8 Ang II binding in neurolysin-deficient mouse brains, however, the extent of reduction was region-specific. The greatest decreases were seen in the cerebral cortex, substantia nigra, hippocampus, paraventricular thalamus, lateral septum, and nucleus accumbens in neurolysin deficient mouse brains. The cerebellar cortex and hypothalamus showed the smallest reductions in 125I-SI Ang II binding. These results verify that the previously-reported novel non-AT1, non-AT2 receptor binding protein, is neurolysin, ut that there may be additional non-AT1 non-AT2 binding sites in the mouse brain. Supported by NHLBI HL-096357.
