A Videomicroscopic Study of the Effect of l-cis-Diltiazem on the Photobehavior of Stentor coeruleus¶

Walerczyk, M; Fabczak, Hanna; Fabczak, S.

doi:10.1562/0031-8655(2003)077<0339:avsote>2.0.co;2

Photochem Photobiol

2003

DOI: 10.1562/0031-8655(2003)077<0339:avsote>2.0.co;2

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A Videomicroscopic Study of the Effect of l-cis-Diltiazem on the Photobehavior of Stentor coeruleus¶

M Walerczyk¹,

Hanna Fabczak²,

S. Fabczak³

Abstract: The protozoan ciliate Stentor coeruleus displays a step-up photophobic response to an increase in light intensity in its environment. The motile response consists of a delayed stop of ciliary beating and transient ciliary reversal period. Such light-avoiding behavior was significantly influenced by an incubation of cells with l-cis-diltiazem, a common blocker of cyclic guanosine monophosphate (cGMP)-gated ion channel conductance. The introduction of l-cis-diltiazem to the medium induced ciliary reversal in con… Show more

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Cited by 3 publications

References 20 publications

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Detection and localization of a putative cyclic-GMP-activated channel protein in the protozoan ciliate Stentor coeruleus

Walerczyk

Fabczak

2006

Protoplasma

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Immunoblotting and immunocytochemical assays were employed to identify and localize a channel protein activated by cyclic GMP (cGMP) in the protozoan ciliate Stentor coeruleus. Analysis of whole-cell homogenate with antibodies raised against the alpha-subunit of the cGMP-activated channel protein from bovine rod outer segments and against cGMP revealed four major protein bands with molecular masses of 40 kDa, 63 kDa, and over 120 kDa, which bound cGMP. However, only a cGMP-binding protein of 63 kDa, corresponding to the alpha-subunit of the cGMP-activated ion channel protein from bovine rod outer segments, was found in the ciliate cortex fraction. The functional cGMP-activated channel protein was also shown to be present in the cortex fraction of S. coeruleus by patch-clamp measurements of artificial liposomes. Incorporation of the cortex fraction into liposomes resulted in the appearance of ion channel activity related to cGMP. The reconstituted protein channels were strongly inhibited by l-cis-diltiazem, a known potent blocker of many types of cyclic-nucleotide-activated channels. The results presented here are the first demonstration of the existence and localization of a putative cGMP-activated channel protein in the ciliate S. coeruleus. Cyclic-nucleotide-activated channel proteins are nonspecific cation channels which mediate the receptor potentials in photoreceptor cells and in cells of the olfactory epithelium. On the basis of these data, we suggest that the 63 kDa protein identified in Stentor coeruleus is also a cGMP-activated ion channel and that it may be involved as an effector in the photosensory transduction pathway leading to the motile photophobic response in this ciliate protist.

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Detection and localization of a putative cyclic-GMP-activated channel protein in the protozoan ciliate Stentor coeruleus

Walerczyk

Fabczak

2006

Protoplasma

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Effect of phosducin silencing on the photokinetic motile response of Blepharisma japonicum

Sobierajska

Joachimiak²,

Bregier

et al. 2011

Photochem Photobiol Sci

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The coloured ciliate Blepharisma japonicum changes swimming velocity (positive photokinesis) and elongates its body in response to a prolonged illumination. We have recently proposed that alterations in the phosphorylation level of the ciliate phosducin (Pdc) may be involved in light-induced cell elongation, which in turn affects the interaction of βγ-dimer of G-proteins (Gβγ) with β-tubulin and subsequent cytoskeletal remodelling. The cellular mechanism that governs the photokinetic effect in this ciliate has not been elucidated. In the present study, we utilise real-time PCR to demonstrate that the levels of ciliate Pdc mRNA are significantly reduced in Pdc-RNAi-treated cells compared to cells fed with bacteria carrying the empty vector (control cells). Using western immunoblotting, we confirmed that these cells treated with Pdc-RNAi expressed a substantially lower level of the Pdc protein. The assay also revealed that in ciliates treated with Pdc-RNAi and exposed to light, the cytosolic level of Gβ (~36 kDa) was reduced, whereas the level of Gβ localized to the membrane (~32 kDa) was increased compared to control cells. In addition, behavioural analysis of the cells indicated a substantial reduction of photokinesis. The findings in this study provide additional characterization of the functional properties of the ciliate Pdc protein and we discuss a likely role for this phosphoprotein in the photokinetic phenomenon of the ciliate protist Blepharisma.

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Photosensitive Signal Transduction Induces Membrane Hyperpolarization in Paramecium bursaria

Mitarai

Nakaoka

2005

Photochem & Photobiology

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The protozoan ciliate Paramecium bursaria exhibits membrane hyperpolarization in response to photostimulation, accompanied with an increased swimming speed. The external addition of cyclic nucleotide phosphodiesterase (PDE) inhibitors, either theophylline (1,3-dimethylxanthine) or 3-isobutyl-1-methylxanthin (IBMX), increased in both amplitudes of the membrane hyperpolarization and the increase in swimming speed. Moreover, the addition of membrane permeable cyclic nucleotide analogs, either 8-bromo-adenosine 3',5'-cyclic monophosphate (Br-cAMP) or 8-Br-guanosine 3',5'-cyclic monophosphate (Br-cGMP), increased these amplitudes. On the other hand, the addition of l-cis-diltiazem, known to block the conductance of cyclic nucleotide-gated channels, partially decreased both amplitudes of the membrane hyperpolarization and the increase in swimming speed. An enzyme immunoassay of cellular cyclic nucleotide contents showed that photostimulation induced a rapid increase in adenosine 3',5'-cyclic monophosphate (cAMP), but little increase in guanosine 3',5'-cyclic monophosphate (cGMP), raising the possibility that a rapid increase in cAMP mediates the light-induced hyperpolarization in P. bursaria.

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A Videomicroscopic Study of the Effect of l-cis-Diltiazem on the Photobehavior of Stentor coeruleus¶

Cited by 3 publications

References 20 publications

Detection and localization of a putative cyclic-GMP-activated channel protein in the protozoan ciliate Stentor coeruleus

Detection and localization of a putative cyclic-GMP-activated channel protein in the protozoan ciliate Stentor coeruleus

Effect of phosducin silencing on the photokinetic motile response of Blepharisma japonicum

Photosensitive Signal Transduction Induces Membrane Hyperpolarization in Paramecium bursaria

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