RESUMO
A fundamental biologic principle is that diverse biologic signals are channeled through shared signaling cascades to regulate development. Large scaffold proteins that bind multiple proteins are capable of coordinating shared signaling pathways to provide specificity to activation of key developmental genes. Although much is known about transcription factors and target genes that regulate cardiomyocyte differentiation, less is known about scaffold proteins that couple signals at the cell surface to differentiation factors in developing heart cells. Here we show that AKAP13 (also known as Brx-1, AKAP-Lbc, and proto-Lbc), a unique protein kinase A-anchoring protein (AKAP) guanine nucleotide exchange region belonging to the Dbl family of oncogenes, is essential for cardiac development. Cardiomyocytes of Akap13-null mice had deficient sarcomere formation, and developing hearts were thin-walled and mice died at embryonic day 10.5-11.0. Disruption of Akap13 was accompanied by reduced expression of Mef2C. Consistent with a role of AKAP13 upstream of MEF2C, Akap13 siRNA led to a reduction in Mef2C mRNA, and overexpression of AKAP13 augmented MEF2C-dependent reporter activity. The results suggest that AKAP13 coordinates Galpha(12) and Rho signaling to an essential transcription program in developing cardiomyocytes.
Assuntos
Proteínas de Ancoragem à Quinase A/metabolismo , Coração Fetal/embriologia , Coração Fetal/metabolismo , Fatores de Troca do Nucleotídeo Guanina/metabolismo , Proteínas de Ancoragem à Quinase A/antagonistas & inibidores , Proteínas de Ancoragem à Quinase A/deficiência , Proteínas de Ancoragem à Quinase A/genética , Sequência de Aminoácidos , Animais , Sequência de Bases , Primers do DNA/genética , Feminino , Coração Fetal/anormalidades , Subunidades alfa G12-G13 de Proteínas de Ligação ao GTP/metabolismo , Regulação da Expressão Gênica no Desenvolvimento , Fatores de Troca do Nucleotídeo Guanina/antagonistas & inibidores , Fatores de Troca do Nucleotídeo Guanina/deficiência , Fatores de Troca do Nucleotídeo Guanina/genética , Hibridização In Situ , Fatores de Transcrição MEF2 , Camundongos , Camundongos Knockout , Microscopia Eletrônica de Transmissão , Antígenos de Histocompatibilidade Menor , Modelos Cardiovasculares , Dados de Sequência Molecular , Miócitos Cardíacos/metabolismo , Fatores de Regulação Miogênica/genética , Fatores de Regulação Miogênica/metabolismo , Gravidez , RNA Interferente Pequeno/genética , Sarcômeros/metabolismo , Sarcômeros/ultraestrutura , Transdução de Sinais , Proteínas rho de Ligação ao GTP/metabolismoRESUMO
OBJECTIVE: To determine the molecular alterations that maintain energy homeostasis in hereditary leiomyomatosis and renal cell cancer (HLRCC) uterine tumors with disrupted fumarate hydratase, compared with nonsyndromic uterine tumors. DESIGN: Laboratory study. SETTING: Tertiary academic university hospital. PATIENT(S): Eleven nonsyndromic leiomyoma-myometrium pairs and three HLRCC leiomyoma-myometrium pairs were obtained from patients who were recruited at national and military research centers in the United States. INTERVENTION(S): Molecular analysis. MAIN OUTCOME MEASURE(S): Hereditary leiomyomatosis and renal cell cancer and nonsyndromic leiomyomas were compared with patient-matched myometrium for relative glycolysis and Krebs cycle gene expression. RESULT(S): By microarray analysis, we confirmed that fumarate hydratase messenger RNA (mRNA) was underexpressed in HLRCC fibroids, compared with matched myometrium. Consistent with the possibility that alterations in fumarate hydratase represented a change to a more anaerobic state, we found that HLRCC fibroids overexpressed genes such as phosphofructokinase, aldolase, phosphoglycerate kinase, enolase, and pyruvate kinase. Expression of these genes was not altered in nonsyndromic leiomyomas. Furthermore, there were no overt changes in expression of Krebs cycle enzyme gene expression, with the exception of fumarate hydratase. CONCLUSION(S): Our findings demonstrate that alterations in fumarate hydratase are compensated for by increases in glycolysis enzyme expression in HLRCC.