Structure, glycosylation, and localization of rat intestinal
guanylyl cyclase c:modulation by fasting.
Scheving, Lawrence A., William E. Russell, and Kang-Mei Chong.
Departments of Pathology, Pediatrics, and Cell Biology, Vanderbilt
University School of Medicine, Nashville, TN 37232-2576
APStracts 3:0121G, 1996.
Guanylyl cyclase (GC) C, an intestinal receptor-guanylyl cyclase,
binds diarrhea producing bacterial ligands such as the Escherichia
coli heat stable enterotoxin (ST). We examined the regulatory
influence of feeding and fasting on the expression, structure, and
biochemical properties of GC-C. When solubilized at 4 C under
nonreducing conditions, GC-C from both fed and fasted rats migrated
on 7% SDS polyacrylamide electrophoretic gels as two extremely large
aggregates that barely penetrated the stacking and resolving gels.
Chemical reduction of disulfide linkages disaggregated GC-C in fed
but not fasted rat samples, causing it to migrate as smaller forms (
220 and 240 kDa). Although GC-C aggregates from fasted rats resisted
this disaggregating effect of chemical reduction, they rapidly
acquired it within 90 min. of refeeding. When solubilized at
denaturing temperatures (95 C) under reducing conditions, GC-C
aggregates largely disassembled into four smaller proteins (Mr.'s:
140,000, 131,000, 85,000, and 65,000). However, the 131 kDa
glycoprotein was disproportionately increased in fasted rat
membranes. This unit and the 220 kDa unit were Endoglycosidase H
sensitive. Subcellular fractionation and immunohistochemical studies
revealed a major redistribution of GC-C from surface to intracellular
enterocyte sites during fasting.
Received 16 August 1995; accepted in final form 1 June 1996.
APS Manuscript Number G360-5.
Article publication pending Am. J. Physiol. (Gastrointest. Liver
Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 28 June 96