Cell Differentiation Section

• Current Research
• Staff
• Selected Publications

Current Research

Epithelial functions of Cdk5

Cdk5 is a member of the cyclin dependent kinase family, known primarily as a regulator of neuronal migration, differentiation, and intercellular communication. However, recent studies have revealed unexpected functions of Cdk5 in a variety of other cell types, including epithelial cells. This laboratory explores Cdk5 functions and their underlying mechanisms in epithelial cells of the eye and seeks to relate these functions to ocular disease.

Previous studies from this laboratory have demonstrated that Cdk5 activity regulates both cell-cell and cell-matrix adhesion in lens and corneal epithelial cells. Moreover, since cell migration depends on coordinated formation and release of cell adhesions, Cdk5 activity also affects the rate of cell migration. Currently, the second major goal of this section of this laboratory is to determine the regulatory pathways that mediate thesefunction of the protein k inase, Cdk5-dependent effects.

To gain some insight into the mechanism of these effects we have performed yeast two hybrid screening of an embryonic rat lens library using Cdk5 or its activating proteins, p35 and p39, as baits. Analysis of interacting clones yielded two novel interacting proteins for p39: muskelin and myosin essential light chain. Both of these proteins are associated with the actin cytoskeleton, suggesting that they may play a role in Cdk5-dependent changes in cell adhesion. Ongoing studies of these protein-protein interactions focus on their possible relationship to epithelial cell migration during lens differentiation.

Another approach we have used to determine Cdk5 function is the generation and analysis of transgenic mice that overexpress Cdk5 or a dominant negative Cdk5 specifically in corneal epithelial cells. Analysis of these animals has shown that Cdk5 regulates corneal epithelial cell migration during wound closure. Further study of this effect has implicated Cdk5 in regulating the activity and localization of activated Src and has raised the possibility that Cdk5 may be a pharmacological target for persistent corneal defects. Animal studies to test this possibility are in progress.

Additional areas of current investigation include the role of Cdk5 in regulating cell-cell adhesion in both the cornea and lens. Experimental approaches include generation of transgenic mice expressing Cdk5 and dominant negative Cdk5 in the lens, proteomic analysis of junction-associated proteins, and TIRF microscopy. Through these and a wide range of other techniques, the Section on Cellular Differentiation hopes to uncover the molecular mechanisms responsible for the physiological effects of in epithelial cells.

Staff

Selected Publications

Ledee DR, Gao CY, Seth R, Fariss RN, Tripathi BK, Zelenka PS. A specific interaction between muskelin and the cyclin-dependent kinase 5 activator p39 promotes peripheral localization of muskelin. J Biol Chem. 2005 Jun 3;280(22):21376-83. PubMed

Zelenka, PS., Regulation of cell adhesion and migration in lens development. Int J Dev Biol. 2004;48(8-9):857-65. Review. PubMed

Gao CY, Stepp MA, Fariss R, Zelenka P. Cdk5 regulates activation and localization of Src during corneal epithelial wound closure. J Cell Sci. 2004 Aug 15;117(Pt 18):4089-98. PubMed

Negash, S., Wang, H.S., Gao, C. Ledee, D., and Zelenka, P. Cdk5 regulates cell adhesion in lens epithelial cells. J. Cell Science 115, 2109-2117, 2002. PubMed

Gao, C.Y., Negash, S. Guo, H.T., Ledee, D., Wang, H.S., and Zelenka P. CDK5 Regulates Cell Adhesion and Migration in Corneal Epithelial Cells. Mol Cancer Res. 1, 12-24, 2002. PubMed