Role of RGD dependent integrins in regulation of cardiac muscle contractility : a dissertation /
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| Format: | Thesis Book |
| Language: | English |
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[College Station, Tex.] :
[Texas A&M University System Health Science Center],
[2005]
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| Abstract: | ABSTRACT: Integrins are considered to play an important role in mechanosensation and mechanotransduction of cardiac myocytes. Based on the role of integrins in cardiac cell mechanobiology, we hypothesized that integrins play a role in the contractile function of the myocardium. To test whether integrins influence cardiac contractile function, the changes in force generated by mouse papillary muscle bundles were measured in the presence and absence of the synthetic integrin-binding peptide GRGDNP (gly-arg-gly-asp-asn-pro). Results demonstrated that in the presence of an RGD containing synthetic peptide, contractile force was significantly depressed by 28% at 4 Hz, 27.7% at 5 Hz and 20% at 10 Hz stimulation frequency (n=6, P<0.01). Treatment of myofibers with either proteolytic fragments of denatured collagen or denatured collagen (Type I), an extracellular matrix protein that contains multiple copies of the RGD motif, also reduced force production significantly. Integrin selectivity of these effects was confirmed in studies utilizing function altering integrin antibodies. It was observed that an integrin-activating antibody for β₁ integrin inhibited the force in a similar way to the synthetic RGD containing peptide, whereas function-blocking antibodies for α₅ and β₁ integrins reversed the effect of the RGD containing peptide. Additionally, the function-blocking antibody for α₅ integrin reversed the effect of proteolytic fragments of denatured collagen on contractile force. In contrast, experiments with a function-blocking antibody for β₃ integrin did not significantly reverse the effect of RGD containing peptide. Collectively, these experiments support a role for the α₅β₁ integrin in cardiac muscle contraction. Determination of the force -[Ca²⁺]i relationship showed that the depressed rate of force generation in the presence of the RGD containing peptide was associated with reduced [Ca²⁺]i. These data indicated that force unit of Ca²⁺ was also reduced significantly, suggesting that the process of myofilament activation was altered. Furthermore, inhibition of protein kinase Ce (PKCe) by the specific inhibitor Ro-32-0432 reversed the activity of RGD containing peptide on papillary muscle bundles. In conclusion, these data indicated that interaction of α₅β₁ integrin with the integrin binding RGD motif depressed the force production in cardiac muscle by altering [Ca²⁺]i and by activating PKCe. |
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| Item Description: | Vita. "Major Subject: Medical Sciences". "Submitted to the Graduate School of Biomedical Sciences of The Texas A&M University System Health Science Center in partial fulfillment for the requirements for the degree of Doctor of Philosophy August 2005." Approved as to style and content by: Gerald A. Meininger, Mariappan Muthuchamy, Robert C. Burghardt, Michael J. Davis, Emily Wilson, Harris J. Granger. |
| Physical Description: | vii, 133 leaves : illustrations ; 28 cm. |
| Bibliography: | Includes bibliographical references (leaves 107-132). |