Collaborative Research: CRCNS Research Proposal: Presynaptic structure-function relationships that control AP waveforms, calcium ion, entry, and transmitter release at NMJs

Nerve cells communicate with each other using travelling electrical pulses called action potentials. These pulses arrive at the end of nerve cells (at structures specialized for chemical communication with neighboring nerve cells called synapses or terminals), where they can trigger electrical pulses in neighboring nerve cells. Despite the fact that these communication events are crucial to everything that the nervous system does, and can be compromised by neural diseases, we know surprisingly little about what shapes the effectiveness of these electrical pulses at synapses, and how diseases change this process. This project uses nerves that cause muscles to contract as a model, and combines physiology and pharmacology measurements in nerve terminals with microscopy to determine the density and distribution of functionally-important proteins. These details are used to development a new computer modeling approach that uses structural and functional information to produce detailed models of electrical pulse generation. The new data and models that project produces will advance basic scientific knowledge about synapse function, and enhance our understanding of the mechanisms that underlie neural disease. The proposed work will also have a broad impact on K-12 education, undergraduate teaching and training, graduate and post-graduate training, community outreach, and science training at under-represented minority institutions.

The presynaptic events that control transmitter release at synapses are incompletely understood, particularly with respect to the role of various ion channels positioned with transmitter release sites (active zones). We hypothesize that the structure-function relationships between active zone ion channels regulates the presynaptic action potential waveform within healthy synapses, and that this relationship is disrupted in disease states. We will approach these issues using a collaborative team of investigators from four universities using an approach broken into four aims: (1) voltage imaging to characterize the shape of the presynaptic action potential, including the effects in disease model synapses, (2) patch clamp measurements of the effects of action potential waveforms on ionic currents, (3) characterization of the density and distribution of presynaptic ion channels in motor nerve terminals using super-resolution imaging, and (4) using a combination of data from prior studies with those collected here, we will develop a novel modeling approach that combines modeling ion channel activation and ion flux in a realistic nerve terminal environment with a voltage simulator that predicts the effects of these ion fluxes on the shape of presynaptic action potentials. The proposed studies will advance basic science issues related to presynaptic function and also enhance understanding of the mechanisms that underlie neuromuscular diseases. Our proposed work will also have a broad impact on K-12 education, undergraduate teaching and training, graduate and postgraduate training, community outreach, training at under-represented minority institutions, and fundamental knowledge about synaptic function.

This grant was cofunded by the Cellular Dynamics and Function Cluster in the Division of Molecular and Cellular Biosciences, and the Division of Emerging Frontiers in the Directorate for Biological Science.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.