The University Logo The University of Melbourne  

Department of Surgery

 Images of Surgery and Surgical Research
Royal Melbourne Hospital and Western Hospital
  

Cell Signalling Laboratory


Lab head: Peter Lock , Ph.D.


Staff
Lab staff and students: Stacey Tchuc Tsing I, B.Sc. (Hons.), Andrew Straffon, Ph.D. Stanley Stylli (M.Sc).

Past students
Craig Smith B.Sc. (Hons.), Ashley Stewart (UROP)

Transformation of a normal cell into a cancer cell requires several chromosomal mutations – including loss-of-function mutations in tumour suppressor genes and gain-of-function mutations in latent oncogenes. Many oncogenes and tumour suppressor genes encode proteins involved in signal transduction – the relay of information from the surface of a cell to cytoplasmic and nuclear targets within it. Research in our laboratory is aimed at defining the nature of the signalling pathways that are regulated by the proteins encoded by the src-family of oncogenes and the spred-family of potential tumour suppressor genes.
We have developed a technique to identify the phosphorylated targets of Src-family tyrosine kinases. (see figure). By identifying and characterising these proteins, we hope to gain a deeper understanding of the mechanisms by which Src-kinases coordinate processes such as cell proliferation. Previously, we identified DokR as a substrate of Src-kinases and found that when phosphorylated, DokR physically associates, via specific binding sites, with the signal relay proteins, RasGAP and Nck, Our studies have shown that DokR can potently inhibit normal T cell development – an activity that is dependent on its ability to interact with RasGAP and Nck.


screening pathway



Recently, we have identified another Src-kinase substrate – ARAP3 – a multi-domain signalling protein that regulates Rho and Arf GTPases. ARAP3 affects membrane and cytoskeletal rearrangements, a function that could impact on cell motility regulation, tumour cell invasiveness and metastasis. We are currently exploring these possibilities as well as investigating how tyrosine phosphorylation of ARAP3 affects its function.

Photomicrograph of fluorescent markers

ARAP3 (green) and F-actin (red) co-localise within
membrane ruffles (yellow) in HEK 293 cell

In the future, we will attempt to identify the substrates of other tyrosine kinases such as the EGF and PDGF receptor tyrosine kinases, which are abnormally activated in tumours of the central nervous system.
Spred proteins are related to the Sprouty-family of proteins, which were first identified in fruit flies as antagonists of growth factor signalling. In mammals, Spred and Sprouty proteins have emerged as key negative regulators of the Ras-MAPK signal transduction cascade – a growth stimulatory pathway that is aberrantly activated in many if not all human cancers. It is possible that Spreds, through their ability to negatively regulate this pathway, may function as tumour suppressor proteins. Our studies, in close collaboration with Dr Christopher Hoven’s group, are aimed at defining the mechanisms underpinning the negative regulatory activity of the Spred proteins. This research has the potential to identify molecules that could be specifically targeted in the future treatments of human diseases..

Recent Publications:

King, J.A., Straffon, A.F., D'Abaco, G.M., Poon, C.L., I, S.T., Smith, C.M., Buchert, M., Corcoran, N.M., Hall, N., Callus, B.A., Sarcevic, B., Martin, D., Lock, P., Hovens, C.M. (2005). Distinct requirements for the Sprouty domain for functional activity of Spred proteins. Biochem J. 388, 445-54.


I, S.T.T, Nie, Z, Stewart, A., Hall, N.E., Najdovska, M., He, H., Randazzo, P.A., and Lock, P. ARAP3 is transiently tyrosine phosphorylated in cells attaching to fibronectin and inhibits cell spreading in a RhoGAP dependent manner. J. Cell Sci. 117, 6071-6084.


Grumont, R, Lock, P., Mollinari, M., Shannon, F., and Gerondakis, S. (2004). The Mitogen-Induced Increase in T Cell Size Involves PKC and NFAT Activation of Rel/NF-?B-Dependent c-myc Expression. Immunity 21, 19-30.
Abud, H.E., Lock, P. and Heath, J.K. (2004). Efficient Gene Transfer Into the Epithelial Cell Layer of Embryonic Mouse Intestine Using Low-Voltage Electroporation. Gastroenterology 126, 1779-1787.


• Gugasyan, R., Quilici, C., I, S.T.T, Grail, D., Verhagen, A.M., Roberts, A., Kitamura, T., Dunn, A.R. and Lock, P. (2002). Dok-Related Protein Negatively Regulates T Cell Development via its RasGTPase-activating Protein and Nck Docking Sites. J Cell Biol. 158, 115-125.


• Verhagen, A.M. and Lock, P. (2002). Revealing the intricacies of Cancer. Genome Biology 3, reports4015.1-4015.5.


• Lawrenson, I.D., Wimmer-Kleikamp, S.H., Lock, P., Schoenwaelder, S.M, Down, M., Reed, C., Boyd, A.W., Alewood, P.F., and Lackmann, M. (2002). Ephrin-A5 induces rounding, cell blebbing and de-adhesion of EphA3 expressing 293T and melanoma cells by CrkII and Rho-mediated signaling. J Cell Sci. 115,1059-72.


• Lock, P., Casagranda, F., and Dunn, A.R. (1999). Independent SH2-binding sites mediate interaction of Dok-related protein with RasGTPase activating protein and Nck. J. Biol. Chem. 274, 22775-22784.


• Lock, P., Abram, C. L., Gibson, T., and Courtneidge, S.A. (1998). A new method for isolating tyrosine kinase substrates used to identify FISH, an SH3 and PX domain-containing protein, and Src substrate. EMBO J. 17, 4346-4357.


• Lock, P., Fumagalli, S., Polakis, P., McCormick, F., and Courtneidge, S.A. (1996). The Human p62 cDNA encodes Sam68 and not the RasGAP-associated p62 protein. Cell 84, 23-4.



Research Support:

The Cell Signalling Laboratory is grateful for the support of the following
funding agencies:

The Friends of The Royal Melbourne Hospital Neuroscience Foundation
James and Linda Wang, Post Doctoral Fellowship

 
Return to the Department of Surgery Main Page
Top of Page

Disclaimer & Copyright : Privacy