Mechanisms of signal transduction in photo-stimulated secretion in Phaeocystis globosa |
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Authors: | Quesada Ivan Chin Wei-Chun Verdugo Pedro |
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Institution: | Department of Bioengineering, University of Washington, Friday Harbor Laboratories, 620 University Road, Friday Harbor, Seattle, WA 98195, USA. |
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Abstract: | Phaeocystis globosa, a leading agent in marine carbon cycling, releases its photosynthesized biopolymers via regulated exocytosis. Release is elicited by blue light and relayed by a characteristic cytosolic Ca(2+) signal. However, the source of Ca(2+) in these cells has not been established. The present studies indicate that Phaeocystis' secretory granules work as an intracellular Ca(2+) oscillator. Optical tomography reveals that photo-stimulation induces InsP(3)-triggered periodic lumenal Ca(2+)] oscillations in the granule and corresponding out-of-phase cytosolic oscillations of Ca(2+)] that trigger exocytosis. This Ca(2+) dynamics results from an interplay between the intragranular polyanionic matrix, and two Ca(2+)-sensitive ion channels located on the granule membrane: an InsP(3)-receptor-Ca(2+) channel, and an apamin-sensitive K(+) channel. |
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Keywords: | ASKCa channel apamin-sensitive Ca2+-sensitive K+ channel InsP3 inositol-1 4 5-trisphosphate [Ca2+]L lumenal Ca2+ concentration [Ca2+]EL extralumenal Ca2+ concentration PLC phospholipase C |
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