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.
Bunda
Severa
S
From the Physiology and Experimental Medicine Program, The Hospital for Sick Children, Department of Laboratory Medicine and Pathobiology, Toronto, Ontario M5G 1X8, Canada.
Wang
Yanting
Y
From the Physiology and Experimental Medicine Program, The Hospital for Sick Children, Department of Laboratory Medicine and Pathobiology, Toronto, Ontario M5G 1X8, Canada.
Mitts
Thomas F
TF
From the Physiology and Experimental Medicine Program, The Hospital for Sick Children, Department of Laboratory Medicine and Pathobiology, Toronto, Ontario M5G 1X8, Canada.
Liu
Peter
P
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.
Arab
Sara
S
Toronto General Hospital/University Health Network, Toronto, Ontario M5G 1X8, Canada.
Arabkhari
Majid
M
From the Physiology and Experimental Medicine Program, The Hospital for Sick Children, Department of Laboratory Medicine and Pathobiology, Toronto, Ontario M5G 1X8, Canada.
Hinek
Aleksander
A
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.
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