Localization of heterotypic gap junctions composed of connexin45 and connexin36 in the rod pathway of the mouse retina

Abstract

The primary rod pathway in mammals contains gap junctions between AII amacrine cells and ON cone bipolar cells which relay the rod signal into the cone pathway under scotopic conditions. Two gap junctional proteins, connexin36 (Cx36) and connexin45 (Cx45), appear to play a pivotal role in this pathway because lack of either protein leads to an impairment of visual transmission under scotopic conditions. To investigate whether these connexins form heterotypic gap junctions between ON cone bipolar and AII amacrine cells, we used newly developed Cx45 antibodies and studied the cellular and subcellular distribution of this protein in the mouse retina. Specificity of the Cx45 antibodies was determined, among others, by Western blot and immunostaining of mouse heart, where Cx45 is abundantly expressed. In mouse retina, Cx45 immunosignals were detected in both plexiform layers and the ganglion cell layer. Double staining for Cx45 and Cx36 revealed a partial overlap in the punctate patterns in the ON sublamina of the inner plexiform layer of the retina. We quantified the distributions of these two connexins in the ON sublamina, and detected 30% of the Cx45 signals to be co-localized with or in close apposition to Cx36 signals. Combining immunostaining and intracellular dye injection revealed an overlap or tight association of Cx36 and Cx45 signals on the terminals of injected AII amacrine and two types of ON cone bipolar cells. Our results provide direct evidence for heterotypic gap junctions composed of Cx36 and Cx45 between AII amacrine and certain types of ON cone bipolar cells.

Electrical synapses between AII amacrine cells in the retina: Function and modulation

“…This seems not to be the case, however, and the current state of knowledge suggests that they contain Cx36 on the AII amacrine side and either Cx36 or Cx45 on the bipolar side (Dedek et al, 2006;Han and Massey, 2005;Lin et al, 2005;Maxeiner et al, 2005). It is still unclear, however, how the individual connexons are assembled on the bipolar side, i.e., to which extent there are both homomeric Cx36 and Cx45 connexons and heteromeric Cx36-Cx45 connexons.…”

Screening of gap junction antagonists on dye coupling in the rabbit retina

“…AII/AII coupling is mediated by Cx36 gap junctions (Feigenspan et al, 2001;Mills et al, 2001) while the coupling between AII amacrine cells and ON cone bipolar cells may rely on heterotypic Cx36/Cx45 gap junctions (Dedek et al, 2006). After dye injecting an AII amacrine cell, a large coupled patch of AII amacrine cells was recovered with an overlying set of cone bipolar cells (Fig.…”

“…In the inner retina, AII amacrine cells of the rod pathway are coupled to other AII amacrine cells via Cx36 gap junctions (Feigenspan et al, 2001;Mills et al, 2001) but they also make heterotypic Cx36/Cx45 gap junctions with ON cone bipolar cells (Han & Massey, 2005;Lin et al, 2005;Maxeiner et al, 2005;Dedek et al, 2006). This pathway has been shown to be essential for the transmission of dark-adapted rod signals through the retinal network (Deans et al, 2002).…”

Connexin 40 Mediates the Tubuloglomerular Feedback Contribution to Renal Blood Flow Autoregulation

“…42 Renin antibody (chicken anti-mouse) was generated by Davids Biotechnologie, Regensburg, Germany. Anti-Cx40 (goat anti-mouse, Santa Cruz, Santa Cruz, CA), anti-Cx37 (rabbit anti-mouse, Alpha Diagnostic International, San Antonio, TX), anti-Cx43 (rabbit anti-mouse, Sigma, St. Louis, MO), and anti-Cx45 (rabbit anti-mouse 43 ) were purchased.…”