Dr Chris Rider

Research interests

1) The Binding of Cytokines Heparin and Heparan Sulfate

Although cytokines, growth factors controlling cell proliferation and differentiation, are small, soluble proteins, they tend to act largely at local tissues sites, i.e. in a paracrine rather than endocrine manner. One mechanism of emerging importance by which locally high concentrations of cytokines are maintained close to their sites of secretion in the tissues, is binding to glycosaminoglycans (GAGs). These are long, unbranched, highly acidic polysaccharides found in the extracellular matrix and on cell surfaces. Our particular interest is to study the GAG binding properties of cytokines of the TGF-β superfamily, which regulate cell proliferation and differentiation. Our recent and current work has focused on three members of this superfamily, GDNF (glial cell line-derived neurotrophic factor), BMP-7 (bone morphogenetic protein-7) and the BMP antagonist, gremlin. Of the four classes of GAG, it is the heparin/heparan sulfate class which have the most variable structures and appear to have the greatest diversity of function.

Our studies of heparin binding make frequent use of a solid phase ELISA technique which we have developed for this purpose. Heparin is covalently coupled to bovine serum albumin, and the resulting complex is absorbed on ELISA plate wells. Cytokine binding is then detected through the use a specific antibody and an appropriate enzyme labeled second antibody. This is a sensitive, quantitative technique of wide applicability in the study of heparin binding proteins. We also have expertise in the selective fragmentation and fractionation of heparin oligosaccharides.

Our overall aim is to determine the biological importance of heparin binding. We use cell culture studies to determine whether this a means of immobilising cytokines and presenting them to high affinity receptors on target cells. We also wish to determine whether heparin binding protects cytokines from proteolysis.

There is considerable interest in the clinical application of recombinant cytokines as therapeutic agents, although the toxicity of systemically administered cytokines is a major problem. A better understanding of the endogenous delivery of secreted cytokines in the tissues is likely to allow for novel strategies to improve cytokine usage. Perhaps recombinant cytokines should be administered pre-bound to carbohydrate vehicles to improve localised delivery. Alternatively better pharmacokinetics may be achieved by modifying recombinant cytokines to enhance or reduce heparin binding.

Recently we studied the cytokine GDNF, a neurotrophic factor of interest in the treatment of advanced Parkinson's disease. We confirmed that this binds strongly to heparin and heparan sulfate, and showed that it does so with an unusual dependence on just one type of sulfate group present in these polysaccharides. Using site-directed mutagenesis we located the site on GDNF responsible for its binding to heparin, and showed that removal of this does not affect the neurotrophic activity of GDNF in simple cell culture (Alfano et al., Biochemical Journal 404:131-140 2007).  Currently we carrying out similar work on the BMP-antagonist protein gremlin, which appears to be important in tissue fibrosis. 

 

Compilation of multiple simulations showing the docking of a heparin oligosaccharide (red and yellow stick representation) on to the basic residue side chains (blue) of the short a-helix (red) of the GDNF polypeptide. Figure courtesy of Prof. Barbara Mulloy, NIBSC.


2) Over-expression of chromosome 1q proteins in breast cancer

It has been known for some time that chromosomal changes in breast cancer frequently result increased copy number of genes located on the q arm of chromosome 1.  The pathological significance of this has yet to be determined.  In collaboration with Dr Mikhail Soloviev we have found that genes in this region are commonly over-expressed at the messenger RNA level.  Does this mean that they are also over-produced at the protein level? If so they might serve as disease markers, and point to novel changes in cellular mechanisms. With the further collaboration of Dr Amanda Harvey (Brunel University) we are going to investigate this possibility

Research group

  • Dr Christopher C. Rider
  • Arnold Junior Nkola Tatsingham, Postgraduate student

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