Alexander Sorkin Associate Professor Pharmacology Ph.D., Institute of Cytology, Academy of Sciences of the U.S.S.R., St. Petersburg Pharmacology UCHSC at Fitzsimons RC1-North, Room 6115 P.O. Box 6511, Mailstop 8303 Aurora, CO 80045 Phone: 303-724-3649 Fax: Email: Alexander.Sorkin@UCHSC.edu

Molecular Basis of of endocytosis and trafficking of growth factor receptors

Mechanisms of endocytosis of epidermal growth factor (EGF) receptor. The focus is on elucidation of the molecular details of the internalization of EGF receptors via clathrin-coated pits and particularly, on specific protein-protein interactions involved in this process. We are currently investigating a role of novel putative EGF receptor binding proteins in receptor trafficking.

Role EGF receptor trafficking in signaling. The interaction of effector proteins (containing SH2 and PTB domains) with EGF receptors occurs immediately upon receptor activation by the ligand at the cell surface. However, receptors remain ligand-occupied, dimerized, activated and phosphorylated after internalization in endosomes. The question to address is when during endocytosis receptors trigger signals and when signaling is terminated. We have developed novel modification of fluorescence resonance energy transfer microscopy technique. This method will be utilized to define cellular localization of EGF receptor interactions with effector proteins in living cells.

Role of clathrin adaptors in cargo recognition and coated pit assembly. We are currently using a unique dominant-negative expression approach to address the role of m subunits of AP2 and AP1 in cargo recognition and formation of coated pits. To this end, tagged ?2 or ?1 subunits bearing mutations of cargo-recognition sites are expressed in tetracycline-dependent manner, so that tagged proteins replace endogenous in the AP2 or AP1 complexes, respectively. GFP-tagged ?2 and ?1 are also employed to study the dynamics of AP complexes in living cells.

Eps15 and CALM. Structure-functional analysis of two components of clathrin-coated pits, Eps15 and CALM (clathrin assembly lymphoid myeloid leukemia protein), will be performed to define the function of these proteins in formation of clathrin-coated vesicles.

Selected Publications

Sorkin A, Von Zastrow M. Signal transduction and endocytosis: close encounters of many kinds. Nat Rev Mol Cell Biol. 2002 Aug;3(8):600-14. Review.

Tebar F, Villalonga P, Sorkina T, Agell N, Sorkin A, Enrich C. Calmodulin regulates intracellular trafficking of epidermal growth factor receptor and the MAPK signaling pathway. Mol Biol Cell. 2002 Jun;13(6):2057-68.

Sorkina T, Huang F, Beguinot L, Sorkin A. Effect of tyrosine kinase inhibitors on clathrin-coated pit recruitment and internalization of epidermal growth factor receptor. J Biol Chem. 2002 Jul 26;277(30):27433-41.

Jiang X, Sorkin A. Coordinated traffic of Grb2 and Ras during epidermal growth factor receptor endocytosis visualized in living cells. Mol Biol Cell. 2002 May;13(5):1522-35.

Schmid SL, Sorkin AD. Days and knights discussing membrane dynamics in endocytosis: meeting report from the Euresco/EMBL Membrane Dynamics in Endocytosis, 6--11 October in Tomar, Portugal. Traffic. 2002 Jan;3(1):77-85.

Latest Publications in PubMed