. An overarching problem in biology is the difficulty in understanding complex levels of integration from genes through systems. Intensive research is conducted at both ends of the spectrum, but there is a dearth of understanding at certain intermediate levels of integration. We address such unexplored levels of integration in nervous systems. First, at the molecular level we address the integration of different ion-channel subunits in heteromeric combinations. Second, at the cellular level we address the myriad neuronal cell types that are differentiated by cell-specific combinations of signaling proteins.
Our first aim i s to identify different neuronal subclasses in mammalian nervous systems, while simultaneously investigating the cell-specific constellations of receptors and ion channels expressed in each subclass. The identification and characterization of different neuronal subclasses is increasingly recognized as an important goal toward understanding integrated brain functions. To this end, we employ calcium imaging of dissociated cells to identify different neuronal cell types by probing their expression of cell-specific receptor- and ion-channel subtypes using selective pharmacological agents. We call this experimental approach, Constellation Pharmacology. Calcium imaging is used because: 1) it is the only viable option for assaying function in >100 neurons simultaneously and 2) changes in cytoplasmic calcium concentration are a common endpoint of nearly all electrical signaling in nervous systems. We started this initiative with sensory neurons because their physiological roles can be determined more easily than neurons from other cell populations (e.g. some neurons mediate sensory modalities that can be assayed in culture). We have extended this research into lower centers of the CNS, such as spinal cord and brainstem, with plans to expand our research to higher centers in the brain.
Our second aim builds upon our knowledge gained in aim 1 for the discovery of new venom peptides with unique targeting-selectivity profiles. Such ligands are, in turn, used to further characterize neuronal subclasses. We demonstrate proof-of-principle that we can use Constellation Pharmacology for discovery of venom peptides that target voltage-gate Na, Ca and K channels.
Project I Relevance. Many diseases of the nervous system are presently intractable, presumably because our understanding of nervous-system complexity is inadequate. We propose an approach to identify specific neuronal cell types and study them. We have tracked changes in a specific neuronal cell type as a function of development, suggesting that we can track changes in specific neuronal cell types as a function of disease, injury, learning or aging.
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