Sarah Hitchcock-DeGregori Professor UMDNJ Department of Neuroscience and Cell Biology Robert Wood Johnson Medical School Room 331 Piscataway. NJ 08854 (732) 235-4528 FAX - 4029 hitchcoc@umdnj.edu

Actin cytoskeleton. coiled coils. protein structure. protein structure-function relationships. contractile and motile function

Molecular mechanisms of function and regulation of the actin cytoskeleton

The actin cytoskeleton underlies nearly every fundamental cellular activity including determination and maintenance of cell shape. intracellular architecture and tissue formation. transport of organelles within the cell and movement of the cells themselves. as well as intracellular and cellular signaling. Long-standing. and continuing biochemical and biophysical research has come together with more recent cellular and genetic experiments to show that tropomyosin is a major cellular regulator of actin filament stability and binding of other proteins to actin that modulate its function. Our goal is to understand the molecular mechanisms underlying the regulation of actin filament contractile and motile function. Research projects range from biophysics and biochemistry to cell biology: Current work includes (1) determination of structures of functional fragments of tropomyosin and tropomyosin binding proteins at atomic resolution using heteronuclear NMR (the work of Dr. Norma Greenfield). (2) analysis of the importance of flexibility for function in coiled coil cytoskeletal proteins. (3) study of the regulation of actin dynamics by proteins that bind to actin including tropomyosin. tropomodulin. and the Arp2/3 complex. and (4) experiments to understand the function of specific tropomyosin isoforms in cells.

Selected Publications

Singh A. Hitchcock-DeGregori SE. (2006) Dual requirement for flexibility and specificity for binding of the coiled-coil tropomyosin to its target. actin. Structure. 14(1):43-50.

Kostyukova AS. Rapp BA. Choy A. Greenfield NJ. Hitchcock-DeGregori SE. (2005) Structural requirements of tropomodulin for tropomyosin binding and actin filament capping. Biochemistry. Mar 29;44(12):4905-10.

Gupton SL. Anderson KL. Kole TP. Fischer RS. Ponti A. Hitchcock-DeGregori SE. Danuser G. Fowler VM. Wirtz D. Hanein D. Waterman-Storer CM. (2005) Cell migration without a lamellipodium: translation of actin dynamics into cell movement mediated by tropomyosin. J Cell Biol. 168(4):619-31.

Greenfield NJ. Kostyukova AS. Hitchcock-DeGregori SE. (2005) Structure and tropomyosin binding properties of the N-terminal capping domain of tropomodulin 1. Biophys J. 88(1):372-83.

Bharadwaj S. Hitchcock-DeGregori S. Thorburn A. Prasad GL. (2004) N terminus is essential for tropomyosin functions: N-terminal modification disrupts stress fiber organization and abolishes anti-oncogenic effects of tropomyosin-1. J Biol Chem. 279(14):14039-48.

Kostyukova AS. Hitchcock-DeGregori SE. (2004) Effect of the structure of the N terminus of tropomyosin on tropomodulin function. J Biol Chem. 279(7):5066-71.

Singh A. Hitchcock-DeGregori SE. (2003) Local destabilization of the tropomyosin coiled coil gives the molecular flexibility required for actin binding. Biochemistry. 42(48):14114-21.

Hitchcock-DeGregori SE. (2003) Now. swing your partner! 3D-domain switching of WASP activates Arp2/3 complex. Nat Struct Biol. 10(8):583-4.

Palm T. Greenfield NJ. Hitchcock-DeGregori SE. (2003) Tropomyosin ends determine the stability and functionality of overlap and troponin T complexes.Biophys J. 84(5):3181-9.

Greenfield. N.J.. Swapna. G.V.T.. Huang. Y.. Palm. T.. Graboski. S.. Montelione. G.T. and Hitchcock-DeGregori. S.E. (2003) The structure of the carboxyl terminus of striated "-tropomyosin in soilution reveals an unusual parallel arrangement of interacting "-helices. Biochemistry 42: 614-619.

Hitchcock-DeGregori. S.E. Song. Y. and Greenfield. N.J. (2002). Functions of tropomyosin's periodic repeats. Biochemistry 41: 15036-15044.

DesMarais. V.. Ichetovkin. I.. Condeelis. J.. and Hitchcock-DeGregori. S.E. (2002). Spatial regulation of actin dynamics: A tropomyosin-free. actin-rich compartment at the leading edge. J. Cell Sci. 115: 4649-4660.

Greenfield. N.J.. Palm. T.. and Hitchcock-DeGregori. S.E. (2002). Structure and interactions of the carboxyl terminus of striated muscle "-tropomyosin: It is important to be flexible. Biophys. J. 83: 2754-2776.

Palm. T.. Graboski. S.. Hitchcock-DeGregori. S.E. and Greenfield. N.J. (2001). Disease-causing mutations in cardiac troponin T: Identification of a critical tropomyosin-binding region. Biophys. J. 81: 2827-2837.

Blanchoin. L.. Pollard. T.D.. and Hitchcock-DeGregori. S.E. (2001). Inhibition of the Arp2/3 complex-nucleated actin polymerization by tropomyosin. Current Biol. 11: 1300-1304.

Greenfield. N.J.. Huang. Y.J.. Palm. T.. Swapna. G.V.T.. Monleon. D.. Montelione. G.T. and Hitchcock-DeGregori. S.E. (2001). Solution NMR structure and folding dynamics of the N-terminus of a rat non-muscle "-tropomyosin in an engineered chimeric protein. J. Mol. Biol. 312: 833-847.

Hitchcock-DeGregori. S.E.. Song. Y.. and Moraczewska. J. (2001). Importance of internal regions and the overall length of tropomyosin for actin binding and regulatory function. Biochemistry 40: 2104-2112.

Moraczewska. J.. Greenfield. N.J.. Liu. Y.. and Hitchcock-DeGregori. S.E. (2000). Alteration of tropomyosin function and folding by a nemaline myopathy-causing mutation. Biophys. J. 79: 3217-3225.

Moraczewska. J.. Nicholson-Flynn. K. And Hitchcock-DeGregori. S.E. (1999) The ends of tropomyosin are major determinants of actin affinity and myosin subfragment 1 induced binding to F-actin in the open state. Biochemistry 38: 15885-15892.