Here is a summary of my project:
TGF-β is a growth factor produced by almost every cell in the body. Its many effects include controlling cell death, inflammation, and cell growth. Due to the fact that TGF-β has so many different effects, the failure of the body to control this protein has been implicated in cancer, emphysema, autoimmune disease and fibrosis of transplanted organs. Although great strides have been made in the prevention of early-onset or acute transplant rejection, later-onset or chronic rejection is still something of a mystery. The presence of TGF-β has been implicated as a cause of this process. It is therefore vitally important to fully understand how TGF-β is regulated after transplantation.
TGF-β is secreted as a complex of proteins containing the inactive (or latent) TGF-β molecule and a TGF-β binding protein known as LTBP. After being secreted by a cell, TGF-β remains bound to the cell surface due to interactions between LTBP and the network of carbohydrate and protein molecules found on most cell surfaces. This network, called the extracellular matrix (or ECM), contains negatively charged molecules called glycosaminoglycans (GAGs) which bind a positively charged part of LTBP, thereby sequestering TGF-β.
In this study, a short LTBP fragment has been produced using genetically engineered bacteria. This fragment is able to bind GAGs in a similar way to full-length LTBP. The fragment also contains a tag so that it can be detected by specific antibodies, and can therefore be used to assess TGF-β binding to cells with varying amounts of ECM as well as to kidney transplant tissue samples from different stages of rejection.
So far it has been shown that this LTBP fragment, named N5, can bind to GAGs attached to a plastic surface. It has also been shown that adding soluble GAGs can remove or “compete” N5 away from the plastic. These GAGs may therefore have a therapeutic role due to their ability to remove TGF-β from graft tissues.
