Project: Research project

Project Details


With the long-term goal of better understanding the roles of the
gastrointestinal peptide hormone secretin in health and disease, the
current proposal focuses on structure, function, and regulation of the
secretin receptor in the exocrine pancreas. Secretin is important
physiologically and is potentially important in the pathogenesis,
diagnosis, and treatment of pancreatic disease. Our general hypothesis
is that structural and regulatory themes active for the secretin
receptor will be distinct from those of the majority of G protein-
coupled receptors, and will provide Insights into the molecular basis
for integrated function of the exocrine pancreas. We propose to follow
complementary pathways directed toward the secretin receptor molecule
and the cellular mechanisms for regulating receptor function. In
preparation, the pancreatic secretin receptor cDNA has been cloned,
sequenced, and expressed; fusion proteins which incorporate tags for
efficient affinity purification of the recombinant receptor have been
constructed and validated; and novel radioligands have been developed.
The secretin receptor cDNA sequence has established its close
relationship to receptors for VIP, PACAP, PTH, and GHRF, and the
absence of structural motifs typical of the majority of G protein-
coupled receptors. The predicted large and complex, cysteine-rich
ectodomains of these receptors interestingly complement the large
pharmacophoric domains of their natural ligands. In this work, we will
characterize the structure of this domain of the receptor, postulating
its key role in agonist binding. This includes analysis of the patterns
of disulfide bonding and glycosylation, and the functional impact of
each. The agonist-binding domain will be defined both directly using
affinity labeling with novel probes incorporating photolabile residues
"intrinsic to" and "spanning" the pharmacophore, and indirectly using
molecular constructs which include deletions, receptor chimeras, and
site-specific mutants. The effects of receptor phosphorylation will be
studied in model recombinant receptor-bearing cell systems, and
mutagenesis approaches will be utilized to define key domains and
residues. Finally, the secretin receptor on the pancreatic acinar cell,
a well-established model for stimulus-activity coupling, will be
studied to define receptor regulatory processes in a prototypic native
cellular environment An understanding of structural and regulatory
themes for the secretin receptor should have broad implications for
this new important receptor family, as well as providing the basis for
exploring the roles of this receptor in normal physiology, in
development, and in the pathogenesis of disease.
Effective start/end date2/1/957/31/15


  • Medicine(all)