Lanping Amy Sung
Professor Emeritus, Bioengineering
Molecular basis of erythrocyte cell membrane mechanics.
Professor Sung focuses on the genomic organization and gene expression of proteins in cellular membrane skeletal structures. Sung uses gene-targeting techniques to identify the functions of individual genes, including in vitro experiments using knockout mouse embryos made with embryonic stem cells. In knockout embryos, genes are deactivated, helping to document the role of specific proteins. Sung is an expert in the proteins that make up the skeletal structure of erythrocytes or red blood cells, including the enzyme transglutaminase and the closely related "pseudo enzyme" Protein 4.2. These seem to trigger alterations in the skeletal structure, perhaps explaining why erythrocytes have a limited life span (an average 120 days in humans). Sung has also delved into the workings of erythrocyte-tropomodulin (E-Tmod), tropomyosin, and actin, three proteins that secure the primary spectrin strands of the skeletal network. Actin provides the glue, but E-Tmod and tropomyosin function as molecular "rulers," enabling the skeletal network to achieve its characteristic hexagonal shape, and also to enlist cellular movement to prune the meshlike network, keeping it trim and springy. Sung is now researching similar meshes in other tissues that, like red blood cells, regularly change shape. Among these are cardio-myocytes, or heart muscles. Sung's research is relevant to the disease phenotypes that result when genes used to build these flexible meshes are lacking or overexpressed. Her research has implications for blood and cardiovascular diseases.
Lanping Amy Sung is principal researcher of the Center for Molecular Genetics, and the Molecular Bioengineering Laboratory. She came to UCSD in 1988 as an associate research bioengineer and lecturer in the Department of Applied Mechanics and Engineering Sciences-Bioengineering. She received her Ph.D. in human genetics and development at Columbia University.
Sung, L.A., Gao, K.-M., Yee, L.J., Temm-Grove, C.J., Helfman, D.M., Lin, J. -J. C., and Mehrpouryan, M.: Tropomyosin isoform 5b is expressed in human erythrocytes: Implications of tropomodulinTM5 or tropomodulin-TM5b complexes in the protofilament and hexagonal organization of membrane skeletons. Blood 95:1473-1480, 2000.
Sung, L.A. and Vera, C.: Protofilament and Hexagon: A 3-D mechanical model for the junctional complex in the erythrocyte membrane skeleton. Ann. Biomed. Eng. 31:1314- 1326, 2003.
Chu, X., Chen, J., Reedy, M, Vera, C., Sung, K.L.P., and Sung, L.A.: E-Tmod capping of actin filaments at the slow growing end is required to establish mouse embryonic circulation. Am. J. Physiol. Heart Circ. Physiol. 284:H1827-H1838, 2003.
Yao, W., and Sung, L.A. Erythrocyte tropomodulin isoforms with and without the N-terminal actinbinding domain. J. Biol. Chem. 285:31408-31414, 2010
Sche, P., Vera, C., and Sung, L.A. Intertwined αβ Spectrin meeting helical actin protofilament in the erythrocyte membrane skeleton: Wrap-around vs. point-attachment. Ann. Biomed. Eng. 39:1984-1993, 2011
Peng, W., and Sung, L.A. RGD-containing ankyrin externalized onto the cell surface triggers αVβ3 integrin-mediated erythrophagocytosis. Biochem. Biophys. Res. Commun. 407:466-471, 2011.