Aldosterone stimulates elastogenesis in cardiac fibroblasts via mineralocorticoid receptor-independent action involving the consecutive activation of Galpha13, c-Src, the insulin-like growth factor-I receptor, and phosphatidylinositol 3-kinase/Akt.
We previously demonstrated that aldosterone, which stimulates collagen production through the mineralocorticoid receptor (MR)-dependent pathway, also induces elastogenesis via a parallel MR-independent mechanism involving insulin-like growth factor-I receptor (IGF-IR) signaling. The present study provides a more detailed explanation of this signaling pathway. Our data demonstrate that small interfering RNA-driven elimination of MR in cardiac fibroblasts does not inhibit aldosterone-induced IGF-IR phosphorylation and subsequent increase in elastin production. These results exclude the involvement of the MR in aldosterone-induced increases in elastin production. Results of further experiments aimed at identifying the upstream signaling component(s) that might be activated by aldosterone also eliminate the putative involvement of pertussis toxin-sensitive Galphai proteins, which have previously been shown to be responsible for some MR-independent effects of aldosterone. Instead, we found that small interfering RNA-dependent elimination of another heterotrimeric G protein, Galpha13, eliminates aldosterone-induced elastogenesis. We further demonstrate that aldosterone first engages Galpha13 and then promotes its transient interaction with c-Src, which constitutes a prerequisite step for aldosterone-dependent activation of the IGF-IR and propagation of consecutive downstream elastogenic signaling involving phosphatidylinositol 3-kinase/Akt. In summary, the data we present reveal new details of an MR-independent cellular signaling pathway through which aldosterone stimulates elastogenesis in human cardiac fibroblasts.
From the Physiology and Experimental Medicine Program, The Hospital for Sick Children, Department of Laboratory Medicine and Pathobiology, Toronto, Ontario M5G 1X8, Canada.
Severa
S
Bunda
From the Physiology and Experimental Medicine Program, The Hospital for Sick Children, Department of Laboratory Medicine and Pathobiology, Toronto, Ontario M5G 1X8, Canada.
Yanting
Y
Wang
From the Physiology and Experimental Medicine Program, The Hospital for Sick Children, Department of Laboratory Medicine and Pathobiology, Toronto, Ontario M5G 1X8, Canada.
Thomas F
TF
Mitts
Heart and Stroke/Richard Lewar Centre for Excellence, University of Toronto, Toronto, Ontario M5G 1X8, Canada; Toronto General Hospital/University Health Network, Toronto, Ontario M5G 1X8, Canada.
Peter
P
Liu
Toronto General Hospital/University Health Network, Toronto, Ontario M5G 1X8, Canada.
Sara
S
Arab
From the Physiology and Experimental Medicine Program, The Hospital for Sick Children, Department of Laboratory Medicine and Pathobiology, Toronto, Ontario M5G 1X8, Canada.
Majid
M
Arabkhari
From the Physiology and Experimental Medicine Program, The Hospital for Sick Children, Department of Laboratory Medicine and Pathobiology, Toronto, Ontario M5G 1X8, Canada; Heart and Stroke/Richard Lewar Centre for Excellence, University of Toronto, Toronto, Ontario M5G 1X8, Canada. Electronic address: alek.hinek@sickkids.ca.
Aleksander
A
Hinek
D000450:Aldosterone / Q000378:metabolism* / Q000494:pharmacology; D002478:Cells, Cultured; D004549:Elastin / Q000235:genetics / Q000378:metabolism; D005347:Fibroblasts / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D044365:GTP-Binding Protein alpha Subunits, G12-G13 / Q000235:genetics / Q000378:metabolism*; D015870:Gene Expression / Q000187:drug effects / Q000502:physiology; D006801:Humans; D009206:Myocardium / Q000166:cytology*; D010455:Peptides; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism*; D016392:Proto-Oncogene Proteins pp60(c-src) / Q000378:metabolism*; D034741:RNA, Small Interfering; D017526:Receptor, IGF Type 1 / Q000378:metabolism*; D018161:Receptors, Mineralocorticoid / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology
D010455:Peptides; D034741:RNA, Small Interfering; D018161:Receptors, Mineralocorticoid; C120583:transfecting peptide I; D000450:Aldosterone; D004549:Elastin; D019869:Phosphatidylinositol 3-Kinases; D017526:Receptor, IGF Type 1; D016392:Proto-Oncogene Proteins pp60(c-src); D051057:Proto-Oncogene Proteins c-akt; D044365:GTP-Binding Protein alpha Subunits, G12-G13