Characterization of nonjunctional hemichannels in caterpillar cells
Department of Entomology, Soils, and Plant Sciences, Clemson University, Clemson, South Carolina 29634-0315,
USA
1Current Address: School of Life Sciences, Yunnan University, Kunming, Yunnan 650091, China
Abstract
Recent studies have demonstrated that hemichannels, which form gap junctions when paired from apposing cells, may serve additional roles when unpaired including cell adhesion and paracrine communication. Hemichannels in mammals are formed by connexins or pannexins, while in insects they are formed by pannexin homologues termed innexins. The formation of functional gap junctions by insect innexins has been established, although their ability to form functional nonjunctional hemichannels has not been reported. Here the characteristics of nonjunctional hemichannels were examined in three lepidopteran cell types, two cell lines (High Five and Sf9) and explanted hemocytes from Heliothis virescens (Fabricius) (Lepidoptera: Noctuidae). Selective fluorescent dye uptake by hemichannels was observed in a significant minority of cells, using fluorescence microscopy and flow cytometry. Carbenoxelone, an inhibitor of mammalian junctions, disrupted dye uptake, while flufenamic acid and mefloquine did not. The presence of Ca2+ and Mg2+ in the media increased hemichannel activity. Additionally, lipopolysaccharide, a stimulator of immune activity in lepidopterans, decreased dye uptake. These results demonstrate for the first time the activity of nonjunctional hemichannels in insect cells, as well as pharmacological tools to manipulate them. These results will facilitate the further examination of the role of innexins and nonjunctional hemichannels in insect cell biology, including paracrine signaling, and comparative studies of mammalian pannexins and insect innexins.
Keywords: gap junction, hemichannel, hemocyte, innexin
Abbreviations: CBX, carbenoxelone; DAPI, 4’-6-Diamidino-2-phenylindole; DCC, divalent cation containing; DCF, divalent cation free; EB, ethidium bromide; FFA, flufenamic acid; HBSS, Hank’s buffered salt solution; LPS, lipopolysaccharide; LY, lucifer yellow; MFO, mefloquine; PI, propidium iodide; RD, rhodamine dextran; SFM, serum free media
Correspondence:
akaijun_luo@ynu.edu.cn,
bturnbul@clemson.edu
Received: 24 September 2010 | Accepted: 8 December 2010 | Published: 18 January 2010
Copyright: This is an open access paper. We use the Creative Commons Attribution 3.0 license that permits unrestricted use, provided that the paper is properly attributed.
ISSN: 1536-2442 | Volume 11, Number 6
Luo K, Turnbull MW. 2011. Characterization of nonjunctional hemichannels in caterpillar cells. Journal of Insect Science 11:6 available online: insectscience.org/11.6
 Figure 1A |
 Figure 1B |
 Figures 2 |
 Figure 3 |
 Figure 4 |