Esther Richler, Ph.D. - US grants

DESCRIPTION (provided by applicant): ATP-gated cationic P2X receptors are widely expressed in neurons and are found on the membrane of hippocampal neurons. Many studies have demonstrated the physiological roles of P2X receptors in hippocampal neurotransmission and plasticity. Thus the electrophysiological properties of native and recombinant P2X channels have been extensively studied. However, little is known about the plasma membrane mobility of P2X channels since receptor mobility cannot be measured with electrophysiological methods. Diffusion of other ligand gated ion channels is known to underlie important physiological processes such as synaptic plasticity and thus P2X receptor mobility is likely an important mechanism in hippocampal physiology. The objective of our work was to develop an imaging approach to monitor P2X receptor mobility in the plasma membrane and to uncover the molecular factors that determine this mobility. Our preliminary data show that different P2X receptors exhibit different levels of mobility, that ATP quickens the rate of receptor mobility and that P2X2 mobility varies in different neuronal compartments. The specific goals of this proposal are 1) to use fluorescence recovery after photobleaching (FRAP) and single particle tracking (SPT) of Quantum dot labelled P2X2 receptees to probe the cellular settings in which P2X2 receptor mobility occurs in hippocampal neurons, 2) to use these measures of mobility to determine the molecular mechanisms that govern P2X2 mobility with a focus on proteins recently shown to interact with the C tail of P2X2. PUBLIC HEALTH RELEVANCE: The results of the research in this proposal are directly relevant to the mission of the NIH since they will lead to a better understanding of how an ion channel found in the brain contributes to hippocampal function, and in turn how the mobility of the channel is affected by neurotransmission in the hippocampus. This is most relevant to epilepsy where P2X2 channels are considered as new drug targets to treat this disease.

DESCRIPTION (provided by applicant): The function of the nervous system is dependent on complex interactions between networks of neurons. Understanding how these networks function in both health and disease is dependent on understanding the function of the fine-scale connections between neurons. The research proposed here is aimed at revealing the functions of specific connections between similar and different types of neurons in the same or different cortical layer. A rabies-based tracing system will reveal the direct monosynaptic connections between neurons in the primary visual cortex of mice. Visual stimulation combined with calcium imaging will then reveal the visual response properties of connected neurons. This method will be the first to simultaneously assess both connectivity and function in a live animal without limitations on the distance between connected cells. The cortical sources and functional contributions of excitatory and inhibitory inputs to single functionally characterized excitatory neurons will be uncovered, and the principles by which a single neuron integrates many inputs to produce a single functional output will be studied. The results of these experiments will shed light on various hypotheses about the functional roles of fine-scale connections in cortical information processing.