Testosterone induces cardiomyocyte hypertrophy through mammalian target of rapamycin complex 1 pathway.

• Abstract: Elevated testosterone concentrations induce cardiac hypertrophy but the molecular mechanisms are poorly understood. Anabolic properties of testosterone involve an increase in protein synthesis. The mammalian target of rapamycin complex 1 (mTORC1) pathway is a major regulator of cell growth, but the relationship between testosterone action and mTORC1 in cardiac cells remains unknown. Here, we investigated whether the hypertrophic effects of testosterone are mediated by mTORC1 signaling in cultured cardiomyocytes. Testosterone increases the phosphorylation of mTOR and its downstream targets 40S ribosomal protein S6 kinase 1 (S6K1; also known as RPS6KB1) and eukaryotic initiation factor 4E-binding protein 1 (4E-BP1). The S6K1 phosphorylation induced by testosterone was blocked by rapamycin and small interfering RNA to mTOR. Moreover, the hormone increased both extracellular-regulated kinase (ERK1/2) and protein kinase B (Akt) phosphorylation. ERK1/2 inhibitor PD98059 blocked the testosterone-induced S6K1 phosphorylation, whereas Akt inhibition (Akt-inhibitor-X) had no effect. Testosterone-induced ERK1/2 and S6K1 phosphorylation increases were blocked by either 1,2-bis(2-aminophenoxy)ethane-N,N,N,N-tetraacetic acid-acetoxymethylester or by inhibitors of inositol 1,4,5-trisphosphate (IP(3)) pathway: U-73122 and 2-aminoethyl diphenylborate. Finally, cardiomyocyte hypertrophy was evaluated by, the expression of beta-myosin heavy chain, alpha-skeletal actin, cell size, and amino acid incorporation. Testosterone increased all four parameters and the increase being blocked by mTOR inhibition. Our findings suggest that testosterone activates the mTORC1/S6K1 axis through IP(3)/Ca(2+) and MEK/ERK1/2 to induce cardiomyocyte hypertrophy.
• Authors: Francisco Altamirano, César Oyarce, Patricio Silva, Marcela Toyos, Carlos Wilson, Sergio Lavandero, Per Uhlén, Manuel Estrada (Affiliation: Facultad de Medicina, Instituto de Ciencias Biomédicas, Centro FONDAP Estudios Moleculares de la Célula, Universidad de Chile, Avenida Independencia 1027, Santiago, Chile.)
• Journal: The Journal of endocrinology (J Endocrinol) Vol. 202 Issue 2 Pg. 299-307 (Aug 2009) ISSN: 1479-6805 [Electronic] England
• PMID: 19474060 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Androgens
• Carrier Proteins
• Eif4ebp1 protein, rat
• Flavonoids
• PD 98059
• Phosphoproteins
• RNA, Small Interfering
• TORC1 protein, rat
• Transcription Factors
• Sirolimus
• Testosterone
• Calcium
• Protein Kinases
• mTOR protein
• S6K1 protein, rat
• Proto-Oncogene Proteins c-akt
• Ribosomal Protein S6 Kinases
• Extracellular Signal-Regulated MAP Kinases

Topics

• Androgens (pharmacology)
• Animals
• Calcium (metabolism)
• Calcium Signaling (physiology)
• Carrier Proteins (metabolism)
• Cells, Cultured
• Enzyme Activation
• Extracellular Signal-Regulated MAP Kinases (antagonists & inhibitors, metabolism)
• Flavonoids (pharmacology)
• Hypertrophy
• Intracellular Membranes (metabolism)
• Myocytes, Cardiac (drug effects, metabolism, pathology)
• Phosphoproteins (metabolism)
• Phosphorylation (drug effects)
• Protein Kinases (genetics)
• Proto-Oncogene Proteins c-akt (metabolism)
• RNA, Small Interfering (pharmacology)
• Rats
• Rats, Sprague-Dawley
• Ribosomal Protein S6 Kinases (metabolism)
• Signal Transduction (physiology)
• Sirolimus (pharmacology)
• Testosterone (pharmacology)
• Transcription Factors (metabolism)