Research in my laboratory
focuses on cell surface receptors and receptor induced signal transduction.
There are two distinct areas of emphasis within this broad field. The
first area comprises receptor mediated changes in intracellular calcium
and tyrosine phosphorylation in the blood platelet, with particular
emphasis on signaling induced by the adhesive protein von Willebrand
factor (VWF). We are also investigating how conformational changes in
VWF enable it to interact with its primary platelet receptor, glycoprotein
Ib IX V (GpIb IX V). The molecular mechanism for interaction between
receptors and G proteins represents the second area of research, with
the emphasis on coupling of the vasoactive intestinal peptide (VIP)
receptor to its associated G proteins in the lung.
Platelets play a
major role in arterial thrombosis. Exposure to an elevated shear stress
in a stenosed artery promotes the interaction of plasma VWF with its
platelet receptor, GpIb IX V. Platelets also adhere through this receptor
to subendothelial VWF that is exposed in a ruptured region of atherosclerotic
plaque. Interaction of VWF with GpIb IX V in either scenario leads to
activation of the platelet. My laboratory is seeking to delineate the
signaling mechanism for such activation. Most of our studies are conducted
on human platelets, using pharmacological inhibitors to block putative
signaling moieties and biochemical techniques to assay signaling intermediates.
In addition, we have recently cloned the complementary DNA (cDNA) for
murine VWF messenger RNA (mRNA) and are developing techniques to study
VWF signaling in mouse platelets. This will allow us to use a genetic
strategy to manipulate molecules with a putative role in the signaling
mechanism. Our current observations suggest that the signaling mechanism
for VWF involves the stimulation of a protein tyrosine kinase, activation
of a novel isozyme of phospholipase A2 and elevation of the intracellular
calcium concentration.
VIP is a potent
bronchodilator with potential therapeutic value in asthma. In conjunction
with Dr. Martin Shreeve at the University of Vermont, my laboratory
has developed a strategy to examine coupling of the VIP receptor to
G proteins in the lung by covalent cross linking of the associated proteins.
This strategy has shown that the VIP receptor associates functionally
with two different G proteins, Gs and Gi3. Domains on the receptor responsible
for association with each G protein are currently under investigation
using this same strategy.
Diehl, N.L., Kermode,
J.C. & Shreeve, S.M. (1996). Direct evidence for functional coupling
of the vasoactive intestinal peptide receptor to Gi3 in native lung
membranes. Molecular Pharmacology, 50, 624 630. 
Kermode, J.C., Zheng,
Q. & Cook, E.P. (1996). Fluorescent indicators give biased estimates
of intracellular free calcium change in aggregating platelets: implication
for studies with human von Willebrand factor. Blood Cells, Molecules,
& Diseases, 22, 238 253.
Milner, E.P., Zheng,
Q. & Kermode, J.C. (1998). Ristocetin mediated interaction of human
von Willebrand factor with platelet glycoprotein Ib evokes a transient
calcium signal: observations with Fura PE3. Journal of Laboratory &
Clinical Medicine, 131, 49 62.
Kermode, J.C., Zheng,
Q. & Milner, E.P. (1999). Marked temperature dependence of the platelet
calcium signal induced by human von Willebrand factor. Blood, 94, 199
207.
Kermode, J.C., Milner,
E.P. & Zheng, Q. (2002). Release from intracellular stores is responsible
for calcium signaling with von Willebrand factor in human platelets.
Thrombosis & Haemostasis, 87, 699 705.
Chitta, M.S., Duhe,
R.J. & Kermode, J.C. (2002). Mus musculus von Willebrand factor
(Vwf) mRNA, complete coding sequence. GenBank submission (accession
number AY208897): National Center for Biotechnology Information, Bethesda,
Maryland; December 30, 2002.
