Colocalization of hyperpolarization-activated, cyclic nucleotide-gated channel subunits in rat retinal ganglion cells

Tyler W. Stradleigh, Genki Ogata, Gloria J. Partida, Hanako Oi, Kenneth P. Greenberg, Kalen S. Krempely, Andrew Ishida

Research output: Contribution to journalArticlepeer-review

20 Scopus citations

Abstract

The current-passing pore of mammalian hyperpolarization-activated, cyclic nucleotide-gated (HCN) channels is formed by subunit isoforms denoted HCN1-4. In various brain areas, antibodies directed against multiple isoforms bind to single neurons, and the current (Ih) passed during hyperpolarizations differs from that of heterologously expressed homomeric channels. By contrast, retinal rod, cone, and bipolar cells appear to use homomeric HCN channels. Here, we assess the generality of this pattern by examining HCN1 and HCN4 immunoreactivity in rat retinal ganglion cells, measuring Ih in dissociated cells, and testing whether HCN1 and HCN4 proteins coimmunoprecipitate. Nearly half of the ganglion cells in whole-mounted retinae bound antibodies against both isoforms. Consistent with colocalization and physical association, 8-bromo-cAMP shifted the voltage sensitivity of Ih less than that of HCN4 channels and more than that of HCN1 channels, and HCN1 coimmunoprecipitated with HCN4 from membrane fraction proteins. Finally, the immunopositive somata ranged in diameter from the smallest to the largest in rat retina, the dendrites of immunopositive cells arborized at various levels of the inner plexiform layer and over fields of different diameters, and Ih activated with similar kinetics and proportions of fast and slow components in small, medium, and large somata. These results show that different HCN subunits colocalize in single retinal ganglion cells, identify a subunit that can reconcile native Ih properties with the previously reported presence of HCN4 in these cells, and indicate that Ih is biophysically similar in morphologically diverse retinal ganglion cells and differs from Ih in rods, cones, and bipolar cells.

Original languageEnglish (US)
Pages (from-to)2546-2573
Number of pages28
JournalJournal of Comparative Neurology
Volume519
Issue number13
DOIs
StatePublished - Sep 1 2011

Keywords

  • HCN
  • Immunohistochemistry
  • Immunoprecipitation
  • Inward rectification
  • Retina

ASJC Scopus subject areas

  • Neuroscience(all)

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