Photoreceptor Synaptic Ribbon Associated Proteins

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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 fivelayers thick. It processes information about light and sends it to the brain.The molecules studied in this research are special proteins in the retinainvolved in signaling the presence or absence of light at the first point atwhich light is detected in the photoreceptor cell. The proteins make up amicroscopic structure in the photoreceptor called the synaptic ribbon.Signals about the presence or absence of light are transmitted to the nextlayer of cells by using the synaptic ribbon in an unknown way. The proposedwork will investigate this mechanism.We have made special markers for this family of proteins. Each markerattaches to proteins with specific weights, which is one of the properties weuse to tell the proteins apart. One of these markers, called the B16antibody, 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 theretina. We will now sequence its amino acids as a way of identifying it andunderstanding the function of this protein. The second group of experiments will examine other proteins are related tothe one recognized by our B16 marker. One of these, called a focal adhesionprotein, may be involved in keeping the synaptic ribbon attached to thepresynaptic membrane. This is the place where information is transmitted tothe next group of cells in the retina.In the third group of experiments we will use the electron microscope to lookat the position of these proteins within the synaptic ribbon. It is criticalthat we demonstrate that the proteins are part of the synaptic ribbon withinthe presynaptic terminal not postsynaptic to the photoreceptor or in theextracellular space. In addition, we will examine the other proteinsassociated with the synaptic ribbon with other biochemical methods. When all the experiments are finished, we expect to have: 1) identified theprotein 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 toa protein that is integral to the synaptic ribbon. This will advance ourfundamental knowledge about what the synaptic ribbon is made of and how itworks.