Levels of Gsα (short and long), Gα olf and Gβ (common) subunits, and calcium-sensitive adenylyl cyclase isoforms (1, 5/6, 8) in post-mortem human brain caudate and cortical membranes: Comparison with rat brain membranes and potential stoichiometric relationships

• Published in: Neurochemistry international Vol. 58; no. 2; pp. 180 - 189
• Main Authors: Zalduegui, Amaia, López de Jesús, Maider, Callado, Luis F., Meana, J. Javier, Sallés, Joan
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 01.02.2011; Elsevier
• Subjects: [3H]-forskolin binding; Adenylyl cyclases isoforms; Biological and medical sciences; Fundamental and applied biological sciences. Psychology; Gsα subunits; Vertebrates: nervous system and sense organs; [3H]-forskolin binding; Adenylyl cyclases isoforms; Gsα subunits; Human; Molecular form; Calcium; Rat; Enzyme; Rodentia; Central nervous system; Electrophysiology; Phosphorus-oxygen lyases; Lyases; Subunit; Encephalon; Adenylate cyclase; Vertebrata; Mammalia; Animal; Membrane potential
• ISSN: 0197-0186; 1872-9754
• DOI: 10.1016/j.neuint.2010.11.014

▶ The stoichiometry has been completed for the Gs-linked AC pathway in human brain. ▶ There is a substantial molar excess of Gsα subunits relative to AC levels. ▶ AC is identified as the most critical component in determining efficacy of the system. The levels of expression of Gsα (short and long), Gα olf and Gβ (common) subunits, and calcium-sensitive adenylyl cyclases isoforms (AC1, 5/6, and 8) in human brain cortical and caudate membranes were quantified by western blot analysis in order to establish their contribution to the patterns of AC functioning. Both areas expressed Gsα long (52 kDa) with values ranging from about 1400 ng/mg of membrane protein in cerebral cortex to close to 600 ng/mg of membrane protein in caudate nucleus. In contrast, Gsα short and Gsα olf were expressed separately, Gsα short in cortical membranes with values around 500 ng/mg of membrane protein and Gα olf in caudate membranes with values around 1300 ng/mg of membrane protein. Quantitative measurements of Gβ, revealed a similar expression level in cortical and caudate membranes (5444 ± 732 versus 5511 ± 394 ng/mg protein; p = 0.966). The B max values of GTPγS-dependent [ 3H]-forskolin binding show the following descending order: rat striatal membranes > rat cortical membranes = human caudate membranes > human cortical membranes. Therefore, as measured immunochemically and by [ 3H]-forskolin binding, there seems to be a vast excess of Gsα subunits over catalytic units of AC. The highest levels of AC5/6 expression were detected in caudate membranes. AC8 was little expressed, and there were no significant differences in the relative values between both human brain regions. Finally, the levels of the AC1 isoform were significantly lower in caudate than in cortical membranes. It is concluded that these stoichiometric data contribute nonetheless to explain the significant differences observed in signalling capacities through the AC system in both human brain regions.