DNA damage induces cell cycle arrest and DNA repair or apoptosis in proliferating cells. Terminally differentiated cells are permanently withdrawn from the cell cycle and partly resistant to apoptosis. To investigate the effects of genotoxic agents in postmitotic cells, we compared DNA damage-activated responses in mouse and human proliferating myoblasts and their differentiated counterparts, the myotubes. DNA double-strand breaks caused by ionizing radiation (IR) induced rapid activating autophosphorylation of ataxia-teleangiectasia-mutated (ATM), phosphorylation of histone H2AX, recruitment of repair-associated proteins MRE11 and Nbs1, and activation of Chk2 in both myoblasts and myotubes. However, IR-activated, ATM-mediated phosphorylation of p53 at serine 15 (human) or 18 (mouse) [Ser15(h)/18(m)], and apoptosis occurred in myoblasts but was impaired in myotubes. This phosphorylation could be enforced in myotubes by the anthracycline derivative doxorubicin, leading to selective activation of proapoptotic genes. Unexpectedly, the abundance of autophosphorylated ATM was indistinguishable after exposure of myotubes to IR (10 Gy) or doxorubicin (1 microM/24 h) despite efficient phosphorylation of p53 Ser15(h)/18(m), and apoptosis occurred only in response to doxorubicin. These results suggest that radioresistance in myotubes might reflect a differentiation-associated, pathway-selective blockade of DNA damage signaling downstream of ATM. This mechanism appears to preserve IR-induced activation of the ATM-H2AX-MRE11/Rad50/Nbs1 lesion processing and repair pathway yet restrain ATM-p53-mediated apoptosis, thereby contributing to life-long maintenance of differentiated muscle tissues.

• MeSH
• aktivace enzymů MeSH
• antibiotika antitumorózní farmakologie   MeSH
• apoptóza fyziologie   MeSH
• ATM protein MeSH
• buněčná diferenciace * fyziologie   MeSH
• buněčné linie MeSH
• checkpoint kinasa 2 MeSH
• DNA vazebné proteiny metabolismus   MeSH
• doxorubicin farmakologie   MeSH
• enzymy opravy DNA MeSH
• fosforylace MeSH
• histony metabolismus   MeSH
• inhibitory enzymů metabolismus   MeSH
• ionizující záření MeSH
• jaderné proteiny metabolismus   MeSH
• koncové značení zlomů DNA in situ MeSH
• lidé MeSH
• myši MeSH
• nádorové supresorové proteiny MeSH
• nádorový supresorový protein p53 genetika   metabolismus   MeSH
• oprava DNA MeSH
• poškození DNA MeSH
• protein-serin-threoninkinasy metabolismus   MeSH
• proteiny buněčného cyklu metabolismus   MeSH
• serin metabolismus   MeSH
• signální transdukce fyziologie   MeSH
• svalové buňky cytologie   fyziologie   účinky léků   účinky záření   MeSH
• zvířata MeSH
• Check Tag
• lidé MeSH
• myši MeSH
• zvířata MeSH

OBJECTIVE: Cardiac hypertrophy is induced by a number of stimuli and can lead to cardiomyopathy and heart failure. Present knowledge suggests that cell-cycle regulatory proteins take part in hypertrophy. We have investigated if the D-type cyclins are involved in cardiac hypertrophy. METHODS: The expression and activity of the D-type cyclins and associated kinases in cardiomyocytes were studied during angiotensin II- and pressure overload-induced hypertrophy in rats (Rattus norvegicus) and in isolated, neonatal cardiomyocytes. Expression of the D-type cyclins was manipulated pharmacologically and genetically in neonatal myocytes. RESULTS: In the left ventricle, there was a low, constitutive expression of the D-type cyclins, which may have a biological role in normal, adult myocytes. The protein level and the associated kinase activity of the D-type cyclins were up-regulated during hypertrophic growth. The increase in cyclin D expression could be mimicked in vitro in neonatal cardiac myocytes. Interestingly, the cyclin Ds were up-regulated by hypertrophic elicitors that stimulate different signalling pathways, suggesting that cyclin D expression is an inherent part of cardiac hypertrophy. Treatment of myocytes with the compound differentiation inducing factor 1 inhibited expression of the D-type cyclins and impaired hypertrophic growth induced by angiotensin II, phenylephrine and serum. The response to hypertrophic elicitors could be restored in differentiation inducing factor 1-treated myocytes by expressing cyclin D2 from a heterologous promoter. CONCLUSION: Our results point to the D-type cyclins as important regulators of cardiac hypertrophy. This supports the notion that cell-cycle regulatory proteins regulate hypertrophic growth.

• MeSH
• angiotensin II MeSH
• cyklin D1 agonisté   analýza   metabolismus   MeSH
• cyklin D2 MeSH
• cyklin D3 MeSH
• cyklin-dependentní kinasy analýza   metabolismus   MeSH
• cykliny analýza   metabolismus   MeSH
• hypertrofie levé komory srdeční * metabolismus   MeSH
• kardiomyocyty metabolismus   účinky léků   MeSH
• krysa rodu rattus MeSH
• kultivované buňky MeSH
• potkani Wistar MeSH
• proteiny Caenorhabditis elegans * MeSH
• proteiny červů farmakologie   MeSH
• signální transdukce * fyziologie   MeSH
• transportní proteiny farmakologie   MeSH
• western blotting metody   MeSH
• zvířata MeSH
• Check Tag
• krysa rodu rattus MeSH
• zvířata MeSH

The Chk2 kinase is a tumor suppressor and key transducer of DNA-damage checkpoints. We show that the human Chk2 protein is relatively stable, nuclear, and responding to gamma-radiation throughout the cell cycle. Contrary to the retinoblastoma protein-regulated, labile Chk1 kinase restricted to S-G(2) phases, Chk2 remains activatable even in quiescent and differentiating cells. In human tissues, Chk2 is homogeneously expressed in renewing cell populations such as epidermis or intestine, heterogeneous in conditionally renewing tissues, and absent or cytoplasmic in static tissues such as muscle or brain. These data highlight striking differences between Chk2 and Chk1 and show unexpected correlation of Chk2 expression with tissue biology.

• MeSH
• aktivace enzymů MeSH
• buněčná diferenciace fyziologie   MeSH
• buněčné dělení fyziologie   MeSH
• buněčné linie MeSH
• buněčný cyklus fyziologie   MeSH
• checkpoint kinasa 2 MeSH
• fibroblasty cytologie   enzymologie   MeSH
• G1 fáze fyziologie   MeSH
• lidé MeSH
• monoklonální protilátky MeSH
• nádorové buňky kultivované MeSH
• osteosarkom enzymologie   patologie   MeSH
• poškození DNA * fyziologie   MeSH
• protein-serin-threoninkinasy * MeSH
• proteinkinasy fyziologie   imunologie   metabolismus   MeSH
• S fáze fyziologie   MeSH
• Check Tag
• lidé MeSH