Studies on plasma membrane proteins of normal and tumor cells

Abstract

Understanding the regulation of cell-proliferation and alterations in the signal transducing newlinemachinery of a cell upon transformation has been the subject of interest for several newlineyears. The eukaryotic cell is compartmentalized into functionally distinct organelles. In newlinemammalian cells, plasma membrane forms the interphase between the cell and its newlinesurrounding environment. Transduction of signals from outside to the interior of a cell newlineis essential for its proper functioning. Many molecules involved in the process of signal newlinetransduction are situated in the plasma membrane. newlineSignal transducing heterotrimeric GTP-binding proteins (G proteins) are important newlinecomponents in coupling a large variety of receptors to second messenger-generating newlinesystems such as adenylyl cyclase, ion channels and phospholipases. These G proteins newlineare situated at the inner surface of the plasma membrane and consist of a, P and the newliney subunits. newlineA number of differences are observed between a normal and a transformed cell. There newlineare perceptible differences at the level of plasma membrane also. Much of the studies newlinein the rece~t past have been concentrated on the roles played by oncogenes and newlineanti-oncogenes in transformation of a cell. There have been very few studies to examine newlinethe role of heterotrimeric GTP-binding proteins (G proteins) in this process. Since G newlineproteins play an important role in the generation of intrac~llular effectors, many PdU3 newlineof which are involved in cell-growth, the role of these proteins in the process of newlinetransformation assumes considerable significance. The involvement of G proteins in newlinemany human diseases has been demonstrated. Mutations in the a subunits of.Q_proteins newlinehave been observed in some human tumors. Also, the studies with mutationally newlineactivated G protein a subunits have revealed the oncogenic potential of these genes. newlineHowever, the role of G protein py subunits in transformation has not been given due newlineattention. This is very important considering the effects of GPr on second messenger newlinegenerating systems.