Photoreceptor Synaptic Ribbon Associated Proteins

Boston College, Chestnut Hill MA

Investigators

Abstract

This research examines molecules in the retina that participate in sight. The retina is a thin sheet of nerve cells at the back of the eye that is five layers thick. It processes information about light and sends it to the brain. The molecules studied in this research are special proteins in the retina involved in signaling the presence or absence of light at the first point at which light is detected in the photoreceptor cell. The proteins make up a microscopic structure in the photoreceptor called the synaptic ribbon. Signals about the presence or absence of light are transmitted to the next layer of cells by using the synaptic ribbon in an unknown way. The proposed work will investigate this mechanism. We have made special markers for this family of proteins. Each marker attaches to proteins with specific weights, which is one of the properties we use to tell the proteins apart. One of these markers, called the B16 antibody, recognizes a rare protein found only in the retina that weighs 54kD. We have recently succeeded in separating the 54kD protein from the rest of the retina. We will now sequence its amino acids as a way of identifying it and understanding the function of this protein. The second group of experiments will examine other proteins are related to the one recognized by our B16 marker. One of these, called a focal adhesion protein, may be involved in keeping the synaptic ribbon attached to the presynaptic membrane. This is the place where information is transmitted to the next group of cells in the retina. In the third group of experiments we will use the electron microscope to look at the position of these proteins within the synaptic ribbon. It is critical that we demonstrate that the proteins are part of the synaptic ribbon within the presynaptic terminal not postsynaptic to the photoreceptor or in the extracellular space. In addition, we will examine the other proteins associated with the synaptic ribbon with other biochemical methods. When all the experiments are finished, we expect to have: 1) identified the protein that our B16 marker recognizes, 2) learned the identity of the other, related proteins in this family, and 3) shown that the B16 marker attaches to a protein that is integral to the synaptic ribbon. This will advance our fundamental knowledge about what the synaptic ribbon is made of and how it works.