Skip to main content
  • Poster presentation
  • Open access
  • Published:

Glycosylation of human receptor guanylyl cyclase C


Post translational modifications regulate several signalling pathways and glycosylation is emerging as a key player in this regulatory process. Glycosylation of cell surface receptors modulate the downstream signalling pathway and when altered causes a change in the normal physiology of the cell [1]. Guanylyl cyclase C (GC-C) belongs to a group of membrane bound receptors that produce the second messenger, cGMP [2]. It is a multi-domain protein in which the extracellular domain (ECD) is N-glycosylated, resulting in the expression of two differentially glycosylated forms of GC-C (130 kDa and 145 kDa) [3]. Apart from the endogenous peptide ligands guanylin and uroguanylin, GC-C is activated by the heat stable enterotoxins (ST) produced by pathogenic Escherichia coli [2]. It is only the 145 kDa form which is activated by ST – a property attributed to the sugars present on it as both forms bind the ligand with comparable affinities as does the non-glycosylated ECD expressed in E. coli [4].

Infection with enteropathogenic E. coli hyperactivates GC-C resulting in diseases such as infant mortality and travellers' diarrhoea in adults. The glycosylation profile in the infant intestine changes with time and diet which perhaps leads to this differential response to ST in infants and adults [5]. Glycosylation is also tissue specific, which may result in differential regulation of GC-C present in extraintestinal tissues [6]. Altered glycosylation in cancer cells [7] may also influence GC-C activity. Thus, this study aims to understand the effect glycosylation has on GC-C function, which may in turn influence cGMP production.


Treatment of cells expressing GC-C with wheat germ agglutinin resulted in inhibition of GC-C activity, while treatment with Concanavalin A did not. This differential response suggests that a specific lectin-sugar interaction prevents receptor activation.

In order to determine the sites of glycosylation responsible for receptor activation, a mutational approach was undertaken. The ten asparagine residues which are putative N-glycosylation sites in the ECD were mutated to alanine. All mutant receptors showed ST-mediated cGMP production in intact cells, but mutations at Asn345 and Asn402 showed a 40% reduction in ST-stimulatability. Western blot analysis of the single mutants showed differences in electrophoretic mobility between mutant and wild type receptors, due to loss of glycosylation.


Apart from activation, glycosylation also protects proteins from proteolytic cleavage. This is significant in the case of GC-C given its localization in the intestinal lumen, where proteolytic enzymes abound. The susceptibility of the N345 mutant to tryptic cleavage revealed that glycosylation may be of physiological importance in the intestinal milieu. Thus the varied roles of glycosylation in GC-C are emerging and the specificity of these roles at different glycosylation sites are being investigated.


  1. Ohtsubo K, Marth JD: Glycosylation in cellular mechanisms of health and disease. Cell. 2006, 126: 855-67. 10.1016/j.cell.2006.08.019.

    Article  CAS  PubMed  Google Scholar 

  2. Schulz S, Green CK, Yuen PS, Garbers DL: Guanylyl cyclase is a heat-stable enterotoxin receptor. Cell. 1990, 63: 941-8. 10.1016/0092-8674(90)90497-3.

    Article  CAS  PubMed  Google Scholar 

  3. Vaandrager AG, Schulz S, De Jonge HR, Garbers DL: Guanylyl cyclase C is an N-linked glycoprotein receptor that accounts for multiple heat-stable enterotoxin-binding proteins in the intestine. J Biol Chem. 1993, 268: 2174-9.

    CAS  PubMed  Google Scholar 

  4. Ghanekar Y, Chandrashaker A, Tatu U, Visweswariah SS: Glycosylation of the receptor guanylate cyclase C: role in ligand binding and catalytic activity. Biochem J. 2004, 379: 653-63. 10.1042/BJ20040001.

    Article  PubMed Central  CAS  PubMed  Google Scholar 

  5. Biol MC, Pintori S, Mathian B, Louisot P: Dietary regulation of intestinal glycosyl-transferase activities: relation between developmental changes and weaning in rats. J Nutr. 1991, 121: 114-25.

    CAS  PubMed  Google Scholar 

  6. Jaleel M, London RM, Eber SL, Forte LR, Visweswariah SS: Expression of the receptor guanylyl cyclase C and its ligands in reproductive tissues of the rat: a potential role for a novel signaling pathway in the epididymis. Biol Reprod. 2002, 67: 1975-80. 10.1095/biolreprod.102.006445.

    Article  CAS  PubMed  Google Scholar 

  7. Dube DH, Bertozzi CR: Glycans in cancer and inflammation – potential for therapeutics and diagnostics. Nat Rev Drug Discov. 2005, 4: 477-88. 10.1038/nrd1751.

    Article  CAS  PubMed  Google Scholar 

Download references

Author information

Authors and Affiliations


Corresponding author

Correspondence to Najla Arshad.

Rights and permissions

Open Access This article is published under license to BioMed Central Ltd. This is an Open Access article is distributed under the terms of the Creative Commons Attribution 2.0 International License (, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Reprints and permissions

About this article

Cite this article

Arshad, N., Visweswariah, S.S. Glycosylation of human receptor guanylyl cyclase C. BMC Pharmacol 9 (Suppl 1), P1 (2009).

Download citation

  • Published:

  • DOI: