The objectives of this proposal are to determine the mechanisms of photoreceptor protein
compartmentalization. Retinal photoreceptors are polarized neurons whose major functions,
include receiving and transmitting signals, are compartmentalized into discrete subcellular
domains. Compartmentalization is critical for normal photoreceptor activity and reduced vision or
blindness result from improper segregation of proteins. Despite their importance, the mechanisms
underlying protein compartmentalization in photoreceptors, or any other neuron, remain poorly
understood. Essential for understanding compartmentalization are the biophysical properties of
the photoreceptor cytoplasm, the biophysical properties of the proteins that are destined to be
compartmentalized and the forces that drive accumulation of proteins, against significant
concentration gradients, into the specific compartments. We have uncovered a fundamental
biophysical mechanism that may be central to protein transport and segregation in all electrically
active cells: transport of charged proteins within the electrical field generated by the photoreceptor
neuronal activity. We call this novel mechanism axial dynamic electrophoretic protein
transport (ADEPT). We will use state of the art live cell fluorescence imaging tools developed in
our lab, powerful transgenic and gene editing techniques in Xenopus, and sophisticated
biochemical and cell biological approaches to address the following aims:
Aim 1: Map the axial cytoplasmic electric field, Eax, in rod photoreceptors.
Aim 2: Determine the impact of ADEPT on photoreceptor protein transport and
compartmentalization in living photoreceptors.
Aim 3: Determine the locations and influence of Arrestin interactions on their distributions
and dynamics in living rods and cones.