Beneficial effects of adenylyl cyclase type 6 (AC6) expression persist using a catalytically inactive AC6 mutant.
Cardiac-directed expression of AC6 has pronounced favorable effects on cardiac function possibly not linked with cAMP production. To determine rigorously whether cAMP generation is required for the beneficial effects of increased AC6 expression, we generated a catalytically inactive AC6 mutant (AC6mut) that has markedly diminished cAMP generating capacity by replacing aspartic acid with alanine at position 426 in the C1 domain (catalytic region) of AC6. Gene transfer of AC6 or AC6mut (adenovirus-mediated) in adult rat cardiac myocytes resulted in similar expression levels and intracellular distribution, but AC6mut expression was associated with marked reduction in cAMP production. Despite marked reduction in cAMP generation, AC6mut influenced intracellular signaling events similarly to that observed after expression of catalytically intact AC6. For example, both AC6 and AC6mut reduced phenylephrine-induced cardiac myocyte hypertrophy and apoptosis (p < 0.001), expression of cardiac ankyrin repeat protein (p < 0.01), and phospholamban (p < 0.05). AC6mut expression, similar to its catalytically intact cohort, was associated with increased Ca2+ transients in cardiac myocytes after isoproterenol stimulation. Many of the biological effects of AC6 expression are replicated by a catalytically inactive AC6 mutant, indicating that the mechanisms for these effects do not require increased cAMP generation.
Department of Medicine, University of California San Diego, Veterans Affairs San Diego Healthcare System, La Jolla, CA 92161, USA. mhgao@vapop.ucsd.edu
Mei Hua
MH
Gao
Tong
T
Tang
Ngai Chin
NC
Lai
Atsushi
A
Miyanohara
Tracy
T
Guo
Rouying
R
Tang
Amy L
AL
Firth
Jason X
JX
Yuan
H Kirk
HK
Hammond
D000262:Adenylyl Cyclases / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D000818:Animals; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology; D019703:Calcineurin / Q000378:metabolism; D002118:Calcium / Q000378:metabolism / Q000502:physiology; D002135:Calcium-Binding Proteins / Q000096:biosynthesis / Q000378:metabolism; D000242:Cyclic AMP / Q000502:physiology; D005786:Gene Expression Regulation / Q000187:drug effects; D006984:Hypertrophy / Q000201:enzymology / Q000503:physiopathology; D009124:Muscle Proteins; D032383:Myocytes, Cardiac / Q000187:drug effects / Q000201:enzymology* / Q000502:physiology; D009687:Nuclear Proteins / Q000378:metabolism; D010656:Phenylephrine / Q000494:pharmacology; D010766:Phosphorylation; D017354:Point Mutation / Q000235:genetics / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012097:Repressor Proteins / Q000378:metabolism; D019210:Troponin I / Q000096:biosynthesis / Q000378:metabolism; D000099211:Phospholamban
D000262:Adenylyl Cyclases; D019703:Calcineurin; D002118:Calcium; D002135:Calcium-Binding Proteins; D000242:Cyclic AMP; D009124:Muscle Proteins; D009687:Nuclear Proteins; D010656:Phenylephrine; D012097:Repressor Proteins; D019210:Troponin I; D000099211:Phospholamban; C491303:Ankrd1 protein, rat; C121100:adenylyl cyclase 6