John E. Rash, PhD
Research Interests -- Freeze-Fracture Immunocytochemistry of Membrane Proteins in Neurons and Glia
Research in this laboratory is conducted in three broad areas:
Immunocytochemical identification of gap junction connexin proteins in neurons and glia in the central nervous system of vertebrates.
Immunogold identification of ion channels and aquaporin water channels in neurons and glia.
Colocalization of accessory proteins in gap junctions and chemical synapses.
Current research centers on the several roles of gap junctions between neurons and between glial cells. In addition to conventional chemical synaptic transmission, the recent discovery of "mixed" (chemical plus electrical) synapses and of pure electrical synapses in the central nervous systems of adult mammals suggest that there are additional or alternative pathways to chemical synapses for intercellular information exchange in the central nervous center. For example, we have recently shown that connexin36 (Cx36) is present in neuronal but not in glia gap junctions, whereas, Cx26, Cx29, Cx30, Cx32, Cx43 and Cx47 are present only in glial gap junctions.
In our studies of connexins and aquaporin water channels in glial cells, we use confocal microscopy and immunocytochemistry, freeze-fracture electron microscopy, and immunogold labeling to correlate structure and function at the subcellular and molecular levels. These studies revealed that "square arrays" in astrocyte and ependymocyte plasma membranes correspond to aquaporin4 water channels.
Li X, Kamasawa N, Ciolofan C, Olson CO, Lu S, Davidson KGV, Yasumura T, Shigemoto R, Rash JE, Nagy JI. 2008. Connexin45-containing neuronal gap junctions in rodent retina also contain connexin36 in both apposing hemiplaques, forming bihomotypic gap junctions, with scaffolding contributed by zonula occludens-1. J Neurosci 29:9769-9789.
Kamasawa N, Furman CS, Davidson KGV, Sampson JA, Magnie AR, Gebhardt BA, Kamasawa M, Yasumura T, Zumbrunnen JR, Pickard GE, Nagy JI, and Rash JE. 2006. Abundance and ultrastructural diversity of neuronal gap junctions in the off and on sublaminae of the inner plexiform layer of rat and mouse retina. Neuroscience 142:1093-1117.
Meier C, Dermietzel R, Davidson KGV, Yasumura T, Rash JE. 2004. Connexin32-containing gap junctions in Schwann cells at the internodal zone of partial myelin compaction and in Schmidt-Lanterman incisures. J Neurosci 24:3186-3198.
Rash JE, Pereda A, Kamasawa N, Furman CS, Yasumura T, Davidson KGV, Dudek FE, Olson C, Nagy JI. 2004. High-resolution proteomic mapping in the vertebrate central nervous system: Close proximity of connexin35 to NMDA glutamate receptor clusters and colocalization of connexin36 with immunoreactivity for zonula occludens protein-1 (ZO-1). J Neurocytol 33:131-152.
Pereda A, Rash JE, Nagy JI, Bennett MVL. 2004. Dynamics of electrical transmission at club endings on the Mauthner cells. Brain Res 47:227-244.
Rash JE, Davidson KGV, Yasumura T, Furman CS. 2004. Freeze-fracture and immunogold analysis of aquaporin-4 (AQP4) square arrays, with models of AQP4 lattice assembly. Neuroscience 129:915-934.
Pereda A, O'Brien J, Nagy JI, Bukauskas F, Davidson KGV, Yasumura T, Rash JE. 2003. Connexin35 mediates electrical transmission at mixed synapses on Mauthner cells. J Neurosci 23:7489-7503.
Rash JE, Yasumura T, Dudek FE, Nagy JI. 2001. Cell-specific expression of connexins, and evidence of restricted gap junctional coupling between glial cells and between neurons. J Neurosci 21:1983-2000.