The research in my laboratory is focused on identifying the molecular components and signaling mechanisms that regulate cytoskeletal protein interactions during heart development. To identify the role of various thin and thick filament associated proteins, primary cultures of chick cardiac myocytes are being used as a model system. Striated muscle is an ideal model system for these studies due to the precise organization and polarity of cytoskeletal components within repeating sarcomeric units (for example, the ~1 mm long actin filaments are easily resolved by light microscopy). Using this system, we can combine morphological and biochemical approaches with direct tests of physiological function.
Recently, we demonstrated that pointed end capping by tropomodulin is required to maintain actin filament length in vivo and that this is essential for contractile function. In addition, our results indicate that separate domains of tropomodulin have different physiological properties. We are presently using two approaches to identify further functional properties of tropomodulin. These include: (1) microinjection of domain-specific, function-blocking antibodies and (2) overexpression of truncated or mutant tropomodulins by cDNA transfection or by microinjection of recombinant tropomodulin fragments.
In the future, to complement the studies described above, the role of tropomodulin and other actin regulatory proteins will be studied in motile cells; that is, in cells where actin filament lengths are maintained at different lengths.
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Gregorio, C.C., C.N. Perry, and A.S. McElhinny. 2005. Functional properties of the titin/connectin-associated proteins, the muscle-specific RING finger proteins (MURFs), in striated muscle. Journal of Muscle Research and Cell Motility 26: 389-400.
McElhinny, A.S., C. Schwach, M. Valichnac, S. Mount-Patrick, and C.C. Gregorio. 2005. Nebulin regulates the assembly and lengths of the thin filaments in striated muscle. Journal of Cell Biology 170: 947-957.
Ono, Y., C. Schwach, P.B. Antin, and C.C. Gregorio. 2005. Disruption in the tropomodulin1 (Tmod1) gene compromises cardiomyocyte development in murine embryonic stem cells by arresting myofibril maturation. Developmental Biology 282: 336-348.
McElhinny, A.S., C.N. Perry, C. Witt, S. Labeit, and C.C. Gregorio. 2004. Muscle-specific RING finger-2 (MURF-2) is important for microtubule, intermediate filament and sarcomeric M-line maintenance in striated muscle development.. Journal of Cell Science 117: 3175-3188.
McElhinny, A., K. Kakinuma, H. Sorimachi, S. Labeit, and C.C. Gregorio. 2002. Muscle-specific RING finger-1 interacts with titin to regulate sarcomeric M-line and thick filament structure and may have nuclear functions via its interaction with glucocorticoid modulatory element binding protein-1. Journal of Cell Biology 157: 125-136.
Kazmierski, S.T., P.B. Antin, C. Witt, A.S. McElhinny, S. Labeit, and C.C. Gregorio. 2003. The complete mouse nebulin gene sequence and the expression of cardiac nebulin. Journal of Molecular Biology 328: 835-846.
Mudry, R.E., C.N. Perry, V.M. Fowler, and C.C. Gregorio. 2003. The interaction of tropomodulin with tropomyosin stabilizes thin filaments in cardiac myocyte. Journal of Cell Biology 162: 1057-1068.
Clark K., A.S. McElhinny, M. Beckerle, and C.C Gregorio. 2002. Striated muscle cytoarchitecture: an intricate web of form and function. Annual Review of Cell and Developmental Biology 18: 637-706.
Bang, M.L., R.E. Mudry, A.S. McElhinny, K. Trombitas, A.J. Geach, R. Yamasaki, H. Sorimachi, H. Granzier, C.C. Gregorio, and S. Labeit. 2001. Myopalladin, a novel 145 kDa sarcomeric protein with multiple roles in Z-disc and I-band protein assemblies. Journal of Cell Biology 153: 413-427.
Gregorio, C.C., and P.B. Antin. 2000. At the heart of myofibril assembly. Trends in Cell Biology 10: 355-362.
McElhinny, A.S., B. Kolmerer, V.M. Fowler, S. Labeit, and C.C. Gregorio. 2000. The N-terminal end of nebulin interacts with tropomodulin at the pointed ends of the thin filaments. Journal of Biological Chemistry 276: 583-592.
