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Lookup NU author(s): Professor John Hesketh
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Under resting conditions, the endoplasmic reticulum (ER) intraluminal free calcium concentration ([Ca2+]ER) reflects a balance between active uptake by Ca2+-ATPases and passive efflux via 'leak channels'. Despite their physiological importance and ubiquitous leak pathway mechanism, very little is known about the molecular nature of these channels. As it has been suggested that the open translocon pore complex of the ER is permeable to ions and neutral molecules, we hypothesized that the ribosome-bound translocon would be permeable to calcium after treatment with puromycin, a translation inhibitor that specifically releases polypeptide chains. At this time, the translocon channel is left open. We measured the fluctuations in cytoplasmic and luminal calcium concentrations using fluorescent dyes (fura-2 and mag-fura-2, respectively). The calcium release induced by thapsigargin (a Ca2+-ATPase inhibitor) was lower after puromycin treatment. Puromycin also reduced the [Ca2+]ER level when perfused into the medium, but was ineffective after anisomycin pre-treatment (an inhibitor of the peptidyl transferase). Puromycin had a similar effect in the presence of heparin and ryanodine. This puromycin-evoked [Ca2+]ER decrease was specific to the translocon. We conclude that the translocon complex is a major calcium leak channel. This work reveals a new role for the translocon which is involved in the control of the [Ca2+]ER and could therefore supervise many physiological processes, including gene expression and apoptosis.
Author(s): Van Coppenolle F, Vanden Abeele F, Slomianny C, Flourakis M, Hesketh J, Dewailly E, Prevarskaya N
Publication type: Article
Publication status: Published
Journal: Journal of Cell Science
Year: 2004
Volume: 117
Issue: 18
Pages: 4135-4142
ISSN (print): 0021-9533
ISSN (electronic): 1477-9137
Publisher: The Company of Biologists Ltd
URL: http://dx.doi.org/10.1242/jcs.01274
DOI: 10.1242/jcs.01274
PubMed id: 15280427
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