Overview   Lab & Research     Rane Lab     My Research       -Neurons       -Ion Channels       -Patch Clamp       -Growth Factors       -PC12 Cells       -Summary   Pseudoscience   Evolution &   Creationism	Growth Factors Growth factors represent a family of proteins that are expressed throughout the central and peripheral nervous system. During the development of the nervous system, their presence is vital for establishing different neuronal types as well as regulating the myriad of connections between neurons and their target cells. In the mature nervous system, growth factors are necessary for the survival of neurons and can regulate neuronal activity. The growth factors that I worked with have been extensively characterized and, indeed, have spawned a host of acronyms that would be the envy of any government agency. These include nerve growth factor (NGF), platelet-derived growth factor (PDGF), basic fibroblast growth factor (bFGF), and epidermal growth factor (EGF). Growth factors, which are found floating about the exterior of cells, act on neurons by binding to receptors, yet another family of proteins expressed in cell membranes. This binding causes two receptors to come together, forming a receptor complex. Receptor coupling activates the domains of the complex that lie within the cell. Once this activation occurs, proteins called intracellular signaling molecules bind to the receptors. These molecules then undergo a biochemical change that, in turn, allows them to activate other signaling molecules. The proteins and events in these biochemical chain reactions are known as intracellular signaling pathways and they provide they basis for most, if not all, types of cellular regulation, including the regulation of ion channels. A diagram of growth factors and some of their signaling pathways is shown below. Scientists have an excellent understanding of which intracellular signaling pathways underlie different cellular events, and a majority of this knowledge has been derived from studies with mutant receptors. These receptors possess mutations that effectively inhibit the receptor from activating specific signaling pathways. Here is how one uses a mutant receptor: Assume that we know a growth factor induces a specific response in a cell. If a growth factor fails to induce the same response in a cell possessing mutated receptors, it's a good bet that the inhibited signaling pathways are essential for the response observed in the normal cell. Well, we've come a long way in explaining the single phrase "intracellular signaling pathways underlying acute and long-term growth factor regulation of neuronal ion channels." We now know what neurons, ion channels, growth factors, and intracellular signaling pathways are. And you might suspect that I'm trying to figure out which intracellular signaling pathways are used by growth factors to regulate the activity of ion channels. If so, then you are correct. But what about this "long-term" and "acute" nonsense? To answer this, we'll examine the cell model that I'm using, the PC12 cell line.
Mind 'Scapes, its pages and contents are © 1998 by Michael D. Hilborn, President of the Biggles 2000 Time-Dimensional Corporation. You are free to copy and use the original artwork on these pages, although I would appreciate it if you ask me first.