GLUCAGON STRUCTURE-FUNCTION STUDIES

The primary goals of this research are to obtain an understanding
of the chemical-physical basis for glucagon structure-biological
activity relationships. We wish to utilize the insights from these
studies to develop glucagon analogues with high receptor
specificity for functionally different glucagon receptors,
especially specific inhibitor (antagonists) of glucagon itself and
of glucagon action. With these analogues we will seek to obtain
a deeper understanding of the role of glucagon in the control of
glucose metabolism and glucose levels in the normal and diabetic
state, and the mechanisms of glucagon action. There is a need for
a better understanding of glucose homeostasis and the mechanisms
that control glucose levels. The specific aims of this research, therefore, are the following.
We will continue to develop the total synthesis approach to
glucagon analogues so as to obtain more potent and prolonged acting
glucagon analogues. Structural and conformational considerations,
including conformational constraints, will be used to develop
glucagon structure-biological activity relationships and to utilize
these results to design more potent, prolonged acting, and receptor
specific glucagon antagonist analogues. We seek to obtain receptor
selective glucagon analogues that will help us to examine more
precisely the multiple transduction mechanisms we have uncovered
for glucagon action. Of special interest are those mechanisms
which appear to be non-cAMP dependent processes. We will develop
the synthetic, analytical, and preparative purification methods so
that high yields of highly purified glucagon analogues can be
obtained. The conformation properties of glucagon analogues,
particularly those that are conformationally constrained and have
unique biological properties, will be examined by biophysical
methods, and the results utilized to develop a working model for
glucagon conformation-biological activity relationships. Further
examination of the mechanism(s) of glucagon activity will be made
using the perifused liver slice system we recently developed
including the effects on cAMP production, cAMP-dependent protein
kinase, Ca+2 efflux and redistribution, glucose release, etc. As
time permits we will further examine a lead we have for a
somatostatin analogue that has high specificity for glucagon-
release inhibition.