Tom Kovala, PhD

 2002-2004

 2001-2004

 1998-2001

1995-1998

1995

1988

1986

1. Regulation of blood vessel formation by sphingosine 1-phosphate

The process of angiogenesis, or new blood vessel formation, is required for tissue repair following injury due to trauma or pathological conditions such as diabetes or a heart attack. Regulation of angiogenesis is a complex process involving multiple factors which may either activate or inhibit the process. Sphingosine 1-phosphate (S1P) is a bioactive phospholipid present in the blood that has recently been demonstrated to act as a potent angiogenic factor. We are studying the signalling pathways activated by S1P in endothelial and smooth muscle cells, the two primary cell types that make up blood vessels. Our current research focuses on cross-talk between the S1P specific G protein-coupled receptors and receptor tyrosine kinases. The molecular mechanisms responsible for this cross-talk and the specific pathways downstream of the tyrosine kinases are being investigated. We have recently demonstrated that the JAK-STAT pathway, a regulator of gene transcription, is activated by cross-talk between these different types of receptors. The roles played by these pathways in regulating cell migration, differentiation and cellular interactions are being examined. By understanding the mechanisms by which blood vessel formation are regulated it will be possible to enhance angiogenesis and facilitate the repair of damaged tissue, or to block the inappropriate angiogenesis associated with tumour formation.

2. Development of ERK inhibitors for cancer treatment

The extracellular signal-regulated kinase (ERK) pathway is central to a variety of cellular processes including proliferation, differentiation and survival. Following cell surface receptor activation, the classical ERK pathway (Ras – Raf – MEK – ERK) is activated. In tumour cells constitutive activation of either receptors, Ras or Raf has frequently been observed and implicated in the development of cancers. Abnormal activation of any of these upstream signalling molecules results in activation of ERK. In turn, ERK activation has been implicated in the ability of tumours to evade both normal growth control and programmed cell death (apoptosis). We have recently identified a novel small molecule inhibitor of ERK kinase activity. In breast cancer cell lines with constitutively active ERK, this inhibitor sensitizes the cells to stress induced apoptosis. We are currently studying the molecular mechanisms by which ERK inhibition sensitizes cells to apoptosis. A second area of research involves the generation of new molecules based on the structure of this inhibitor and 3-dimensional molecular modeling of the ERK structure. Currently there are no direct inhibitors of ERK activity available and the development such compounds has the potential to be of great clinical utility in the treatment of tumours.

Boguslawski, G., McGlynn, P.W., Harvey, K.A., Kovala, A.T. (2004) SU1498, an inhibitor of vascular endothelial growth factor receptor 2, causes accumulation of phosphorylated ERK kinases and inhibits their activity in vivo and in vitro. Journal of Biological Chemistry 279:5716-5724

Harvey, K., Welsh, Z., Kovala, A.T., Garcia, J.G.N., and English, D. (2002) Comparative analysis of in vitro angiogenic activities of endothelial cells of heterogeneous origin. Microvascular Research 63:316-326

Boguslawski, G., Grogg, J.R., Welch, Z., Ciechanowicz, S., Sliva, D., Kovala, A.T., McGlynn, P., Brindley, D.N., Rhoades, R.A., and English, D. (2002) Migration of Vascular Smooth Muscle Cells Induced by Sphingosine 1-Phosphate and Related Lipids: Potential Role in the Angiogenic Response. Experimental Cell Research 274(2):264-274

Kovala, A.T., Harvey, K., McGlynn, P., Boguslawski, G., Garcia, J.G.N., and English, D. (2000) High efficiency transient transfection of endothelial cells for functional analysis. FASEB Journal 14:2486-2494

English, D., Welsh, Z., Kovala, A.T., Harvey, K., Volpert, O.V., Brindley, D. and Garcia, J.G.N. (2000) Sphingosine 1-phosphate released from platelets during clotting accounts for the potent endothelial cell chemotactic activity of blood serum and provides a novel link between blood hemostasis and angiogenesis. FASEB Journal 14:2255-2265

Boguslawski, G., Lyons, D., Harvey, K.A., Kovala, A.T., and English, D. (2000) Sphingosylphosphorylcholine induces endothelial cell migration and morphogenesis. Biochemical and Biophysical Research Communications 272(2):603-609

English, D., Kovala, A.T., Welch, Z., Harvey, K.A., Siddiqui, R.A., Brindley, D.N., and Garcia, J.G.N. (1999) Induction of endothelial cell chemotaxis by sphingosine 1-phosphate and stabilization of endothelial monolayer barrier function by lysophosphatidic acid, potential mediators of hematopoietic angiogenesis. Journal of Hematotherapy and Stem Cell Research 8:627-634

Harvey, K., Siddiqui, R.A., Reeves, M., Kovala, T., Dugan, M., Akard, L., and English, D. (1999) Characterization and partial purification of CD34+ progenitor cell ecto-phosphatidic acid phosphohydrolase. Biochemistry and Molecular Biology International. 47:9-23

Kovala, T., Sanwal, B.D., and Ball, E.H. (1997) Recombinant expression of a Type IV, cAMP-specific phosphodiesterase: Characterization and structure-function studies of deletion mutants. Biochemistry 36:2968-2976

Kovala, T., Lorimer, I.A.J., Brickenden, A.M., Ball, E.H., and Sanwal, B.D. (1994) Protein kinase A regulation of cAMP phosphodiesterase expression in rat skeletal myoblasts. Journal of Biological Chemistry 269:8680-8685