GATA4 is a survival factor in adult cardiac myocytes but is not required for alpha1A-adrenergic receptor survival signaling.
Recently, we defined an alpha1A-adrenergic receptor-ERK (alpha1A-AR-ERK) survival signaling pathway in adult cardiac myocytes. Previous studies in neonatal cardiac myocytes indicated that the cardiac-specific transcription factor GATA4 is a downstream mediator of alpha1-ERK signaling and that phosphorylation of GATA4 by ERK increases DNA binding and transcriptional activity. Therefore, we examined GATA4 as a potential downstream effector of alpha1A-ERK survival signaling in adult cardiac myocytes. We measured norepinephrine (NE)-induced cell death in cultured cardiac myocytes lacking alpha1-ARs (cultured from alpha1A/B-AR double-knockout mice, alpha1ABKO mice) that are susceptible to cell death induced by several proapoptotic stimuli, including NE. Our results show that overexpression of GATA4 is sufficient to protect alpha1ABKO cardiac myocytes from NE-induced cell death. However, we found that the alpha1A-subtype did not induce phosphorylation or increase the activity of GATA4 in adult mouse cardiac myocytes in culture or in vivo. Furthermore, we examined the effect of siRNA-mediated knockdown of GATA4 on alpha1A-survival signaling. In alpha1B-knockout cardiac myocytes, which express only the alpha1A-subtype and are protected from NE-induced cell death, GATA4 knockdown did not reverse alpha1A-survival signaling in response to NE. In summary, we found that GATA4 acted as a survival factor by preventing cell death in alpha1ABKO cardiac myocytes, but GATA4 was not activated by alpha1-AR stimulation and was not required for alpha1A-survival signaling in adult cardiac myocytes. This also identifies an important mechanistic difference in alpha1-signaling between adult and neonatal cardiac myocytes.
Huang
Yuan
Y
Cardiovascular Research Center, Sanford Research/Univ. of South Dakota, Dept. of Internal Medicine, Univ. of South Dakota, 1100 E. 21st St., Ste. 700, Sioux Falls, SD 57105, USA.
Wright
Casey D
CD
Kobayashi
Satoru
S
Healy
Chastity L
CL
Elgethun
Megan
M
Cypher
Andrew
A
Liang
Qiangrong
Q
O'Connell
Timothy D
TD
D000367:Age Factors; D000818:Animals; D017209:Apoptosis; D002311:Cardiomyopathy, Dilated / Q000378:metabolism / Q000473:pathology; D002462:Cell Membrane / Q000378:metabolism; D002470:Cell Survival; D002478:Cells, Cultured; D019610:Cytoprotection; D004195:Disease Models, Animal; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D050991:GATA4 Transcription Factor / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D008297:Male; D051379:Mice; D018345:Mice, Knockout; D032383:Myocytes, Cardiac / Q000201:enzymology / Q000378:metabolism* / Q000473:pathology; D009638:Norepinephrine / Q000378:metabolism*; D010766:Phosphorylation; D034622:RNA Interference; D034741:RNA, Small Interfering / Q000378:metabolism; D018340:Receptors, Adrenergic, alpha-1 / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D015398:Signal Transduction; D014162:Transfection
C547713:ADRA1A protein, human; C547716:ADRA1B protein, human; C547714:Adra1a protein, mouse; C547717:Adra1b protein, mouse; D050991:GATA4 Transcription Factor; C484171:Gata4 protein, mouse; D034741:RNA, Small Interfering; D018340:Receptors, Adrenergic, alpha-1; D011993:Recombinant Fusion Proteins; D048049:Extracellular Signal-Regulated MAP Kinases; D009638:Norepinephrine