Cardiomyocyte hypertrophy induced by angiotensin II (AngII) is mediated by the type 1 AngII receptor (AT1R). Activated AT1Rs promote growth by transactivating epidermal growth factor receptors (EGFRs), presumably via shedding of EGF-like ligands and the activation of one or more EGFR family members (four structurallyconserved receptor tyrosine kinases exist, termed ErbB1-4). Screening a panel of EGF-like ligands for their capacity to induce cardiomyocyte hypertrophy (measured by changes in protein:DNA ratio) revealed that betacellulin, neuregulin1-β1 and neuregulin2β (which predominantly act through ErbB4) were the most potent activators (147.9±1.6, 134.6±2.0, and 133.7±2.1% compared to control, respectively). No small molecule selective inhibitors of ErbB4 are available, so we have developed small interfering RNAs that target ErbB4 gene expression (ErbB4 siRNA) to allow examination of the requirement for ErbB4 in cardiomyocyte hypertrophy. Interestingly, four major splice variants of ErbB4 exist and we used RT- PCR to show that these are all expressed in cardiomyocytes. Hence, we designed our siRNA to target a common region of the ErbB4 mRNA sequence and then confirmed this in HEK293 cells transiently expressing the separate ErbB4 isoforms. Using promoter-driven luciferase constructs for genes related to cardiomyocyte growth (ANP, MLC2V and cyclinD), we observed that panknockdown of ErbB4 prevented the ability of neuregulin1/AngII to selectively activate ANP, CycD and MLC2V. This decrease was reversed by co-expression of specific ErbB4 isoforms mutated to make them resistant to siRNA knockdown, confirming that ErbB4 appears to mediate AngII-dependent cardiomyocyte hypertrophy and that this is mediated in an isoform-specific manner.

Angiotensin II signals to cardiomyocyte growth pathways via ErbB4.

GAMBAROTTA, Giovanna;
2007

Abstract

Cardiomyocyte hypertrophy induced by angiotensin II (AngII) is mediated by the type 1 AngII receptor (AT1R). Activated AT1Rs promote growth by transactivating epidermal growth factor receptors (EGFRs), presumably via shedding of EGF-like ligands and the activation of one or more EGFR family members (four structurallyconserved receptor tyrosine kinases exist, termed ErbB1-4). Screening a panel of EGF-like ligands for their capacity to induce cardiomyocyte hypertrophy (measured by changes in protein:DNA ratio) revealed that betacellulin, neuregulin1-β1 and neuregulin2β (which predominantly act through ErbB4) were the most potent activators (147.9±1.6, 134.6±2.0, and 133.7±2.1% compared to control, respectively). No small molecule selective inhibitors of ErbB4 are available, so we have developed small interfering RNAs that target ErbB4 gene expression (ErbB4 siRNA) to allow examination of the requirement for ErbB4 in cardiomyocyte hypertrophy. Interestingly, four major splice variants of ErbB4 exist and we used RT- PCR to show that these are all expressed in cardiomyocytes. Hence, we designed our siRNA to target a common region of the ErbB4 mRNA sequence and then confirmed this in HEK293 cells transiently expressing the separate ErbB4 isoforms. Using promoter-driven luciferase constructs for genes related to cardiomyocyte growth (ANP, MLC2V and cyclinD), we observed that panknockdown of ErbB4 prevented the ability of neuregulin1/AngII to selectively activate ANP, CycD and MLC2V. This decrease was reversed by co-expression of specific ErbB4 isoforms mutated to make them resistant to siRNA knockdown, confirming that ErbB4 appears to mediate AngII-dependent cardiomyocyte hypertrophy and that this is mediated in an isoform-specific manner.
3rd Barossa Meeting "Signalling Systems"
Barossa Valley (South Australia)
14-17 novembre 2007
3rd Barossa Meeting Abstracts
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http://www.sapmea.asn.au/conventions/signallingsystems/index.html
Chan H-W; Smith NJ; Agrotis A; Gambarotta G; Hannan RD; Walter Thomas WG
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/2318/68881
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