Effect of chronic ethanol treatment of Ca2+-inhibited adenylyl cyclase in mouse striatum

Isoform-specific enhancement of adenylyl cyclase activity by n-alkanols

BACKGROUND

Numerous studies suggest that cAMP signaling pathways play important roles in the development of and predisposition to alcoholism. Our previous study showed that cAMP generation by various isoforms of adenylyl cyclase (AC) exhibits a broad spectrum of responses to ethanol in the human embryonic kidney (HEK) 293 cell system overexpressing individual AC isoforms. These findings suggest that the target of ethanol's action in the cAMP-generating system is AC. However, it is unknown if the action of ethanol is direct or indirect.

METHODS

The effect of a series of n-alkanols (ethanol to decanol) on dopamine (DA)-stimulated activity of AC isoforms type 6, 7, and 9 (AC6, AC7, and AC9) were examined in transfected HEK293 cells by cAMP accumulation assay.

RESULTS

n-Alkanols increased DA-stimulated cAMP production in an AC isoform-specific manner, and displayed the alcohol cutoff phenomenon (defined as the carbon chain length beyond which there is no further increase in the potency of an ascending series of n-alkanols). The n-alkanol cutoffs for AC6, AC7, and AC9 are butanol (C4), pentanol (C5), and equal to or greater than decanol (C10), respectively.

CONCLUSION

The results clearly indicate that, in the HEK293 expression system, the alcohol cutoff effect for n-alkanol potentiation of DA-stimulated AC activity is AC isoform specific. These results strongly suggest that alcohols interact directly with AC molecules.

Regulation of adenylyl cyclase in the central nervous system

Adenylyl cyclases (ACs) are a family of enzymes that synthesize one of the major second messengers, cAMP, upon stimulation. Since the report of the first adenylyl cyclase (AC) gene in 1989, tremendous efforts have been devoted to identifying and characterizing more AC isozymes. In the past decade, significant knowledge regarding the basic structure, tissue distribution, and regulation of AC isozymes has been accumulated. Because members of the AC superfamily are tightly controlled by various signals, one of the most important impacts of these AC isozymes is their contribution to the complexity and fine-tuning of cellular signalling, especially in the central nervous system (CNS) where multiple signals constantly occur. This review focuses on recent progress toward understanding the physiological roles of ACs in the CNS.