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Isolation and expression of a guanylate cyclase-coupled heat stable enterotoxin receptor cDNA from a human colonic
Abstract:
Heat stable enterotoxins (STs) are low molecular-weight peptides secreted by enterotoxigenic bacteria. One type of these enterotoxins (STa) induces intestinal secretion leading to acute diarrhea by binding to a membrane form of guanylate cyclase. We have isolated a cDNA from a human colonic cell line, T84, encoding for a guanylate cyclase-coupled enterotoxin receptor (STaR). The predicted amino acid sequence of the human STa receptor is 81% identical with the previously cloned enterotoxin receptor (GC-C) from rat intestine. COS-7 cells transiently transfected with the cloned cDNA expressed specific concentration-dependent response to STa as measured by cyclic GMP accumulation and is about 20 times more sensitive to the stimulation by STa than has been shown for GC-C.
Insights
Researchers identified a human receptor for heat-stable enterotoxins (STa). This guanylate cyclase-coupled enterotoxin receptor (STaR) is crucial for understanding bacterial toxin interactions and developing treatments for diarrhea.
Area of Science:
- Molecular biology
- Gastroenterology
- Microbiology
Background:
- Heat-stable enterotoxins (STs) are bacterial peptides causing diarrhea.
- STa toxins activate guanylate cyclase, leading to intestinal secretion.
- Understanding the STa receptor is key to addressing ST-induced diarrhea.
Purpose of the Study:
- To isolate and characterize the human receptor for STa enterotoxins.
- To investigate the functional properties of the human STa receptor.
Main Methods:
- cDNA isolation from human T84 colonic cells.
- Gene cloning and expression in COS-7 cells.
- Measurement of cyclic GMP accumulation in response to STa.
Main Results:
- Isolated a cDNA encoding the human guanylate cyclase-coupled enterotoxin receptor (STaR).
- Human STaR shares 81% amino acid identity with the rat GC-C receptor.
- Transfected cells showed STa-specific, concentration-dependent cyclic GMP accumulation.
- Human STaR is approximately 20-fold more sensitive to STa than rat GC-C.
Conclusions:
- The cloned STaR represents the functional human receptor for STa enterotoxins.
- Human STaR exhibits enhanced sensitivity to STa compared to its rat counterpart.
- This discovery provides a molecular target for combating ST-induced diarrhea.