A mutant of <i>Paramecium</i> with increased relative resting potassium permeability

Satow, Youko; Kung, Ching

doi:10.1002/neu.480070405

Cited by 34 publications

(22 citation statements)

References 31 publications

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“…The increase of external concentration of these cations depolarize the resting membrane. On the other hand, the K-permeability is considered the major permeability of the resting membrane in P. caudatum (Naitoh and Eckert, 1968a;Eckert, Naitoh and Machemer, 1976) and P. tetraurelia (Satow and Kung, 1976a). The present work supports the latter view.…”

Section: Discussionsupporting

confidence: 84%

Internal calcium concentration and potassium permeability in Paramecium

Satow

1978

J. Neurobiol.

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Ca or EGTA was ionophoretically injected into Paramecium tetraurelia to change [Ca]i. Ca decreased the resting membrane resistance and hyperpolarized the membrane. EGTA had the opposite effect. EGTA following TEA, which suppress GK, had little effect on resistance or resting potential. The I-V relation at steady state was studied before and after EGTA injection while the cell bathed in either K- or TEA-solution. The response to inward test pulses after EGTA injection was similar to that after TEA injection. These results show that [Ca]i controls a steady-state K permeability in Paramecium tetraurelia. A prolonged Ca-spike was recorded after EGTA injection. The plateau potentials in various Ca concentrations in a TEA-solution show the Nernst slope (29 mV for tenfold change in [Ca]o). This result suggests that the prolonged depolarization in this condition is due to a Ca current, after suppression of K-permeability and when [Ca]i is low. The difficulty of obtaining quantitative data on the internal Ca, and the difference between the effects of EGTA injection and TEA injection are discussed.

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Section: Discussionsupporting

confidence: 84%

Internal calcium concentration and potassium permeability in Paramecium

Satow

1978

J. Neurobiol.

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“…Despite the loss of attraction in Na-acetate, we believe that I Na(Ca) plays no significant role in chemoresponse to acetate because the loss of chemoresponse in K + -free (Na) acetate solutions is a secondary effect of the mutation. Cam 11 in K + -free media has an extremely low resting membrane potential [near the equilibrium potential for K + (E K ) (Satow and Kung, 1976)], which prevents the cell from responding with an adequate hyperpolarization for the on-response or depolarization of the off-response.…”

Section: Acetate T-mazesmentioning

confidence: 99%

Genetic dissection of attractant-induced conductances inParamecium

Bell

Preston

Yano

et al. 2007

Journal of Experimental Biology

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behaviors of fast swimming with few turns, and the mutants' behavior suggests that I K(Ca,h) is the conductance involved that initiates this behavior. I K(Ca,h or d) appears to be important to the on-response in biotin; the results with mutants suggest that the biotin off-response depolarization is initiated by an I Ca , which can be large enough or close enough to channels to open I K(Ca,d) , I Na(Ca) and I Mg(Ca).

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“…Three of these (spots B, D, and F) are phosphonolipids, and the other three (spots A, C, and E) have the more common phosphodiester linkages at the headgroup. It appears most likely that the three pairs (spots A and B, C and D, and E and F) represent the phospholipid and phosphonolipid derivatives of three long-chain bases, sphingosine, dihydrosphingosine, and phytosphingosine (21 (30). The baAffna double mutant showed the same alteration ofciliary membrane phospholipid and sphingolipid composition as did the baA single mutant (Table 1).…”

Section: Resultsmentioning

confidence: 90%

“…Furthermore, over 300 behavioral-mutant lines have been isolated mapping to more than 25 complementation groups (26,27). The electrophysiological correlates of these behavioral mutations have, in many cases, been determined (28)(29)(30) (33), and hydrostatic pressure (34) have suggested that lipids also affect ion channel activity in Paramecium. In this report we now show that the functions ofvoltage-sensitive ion channels in the excitable membrane of Paramecium appear to be affected by a mutationally induced change in the phospholipid composition of the ciliary membrane.…”

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Mutational alteration of membrane phospholipid composition and voltage-sensitive ion channel function in paramecium.

Forte¹,

Satow²,

Nelson³

et al. 1981

Proc. Natl. Acad. Sci. U.S.A.

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A behavioral mutant of Paramecium tetraurelia (baA) has been isolated that has an abnormal response when placed in solutions containing Ba2+. This mutant is shown here to have a dramatic alteration of the sphingolipid and phosphonolipid composition ofits ciliary membrane. This biochemical defect is present in independently isolated alleles at baA locus and segregates in crosses with the behavioral phenotype. Electrophysiologically, the mutation reduces significantly conductance of both voltage-sensitive Ca2+ channels and voltage-sensitive K+ channels. When the mutant is grown in sterol-supplemented medium, its behavior, electrophysiological properties, and lipid composition are hardly distinguishable from wild type grown under similar conditions. This mutant then, provides strong evidence that membrane lipids significantly influence the function of the membrane molecules responsible for the generation of action potentials.Many membrane enzymatic and transport functions have been shown to be modulated by the membrane lipid composition (1-3). The membrane proteins responsible for the generation of action potentials are similar to those with enzymatic activity in that their function is influenced by membrane lipids as inferred from indirect studies on the effects of temperature (4), enzyme digestions (5-9), and the application of agents (e.g., local anesthetics or pressure), which are expected to alter the physical properties of membrane lipid (10-13).The ciliated protozoan Paramecium tetraurelia is well suited to the study ofthe molecular basis ofmembrane excitability. The cilia of Paramecium are covered by a membrane that is continuous with the body surface membrane (14). Membrane depolarization causes these channels to open allowing an influx of Ca2+, which increases transiently the intracellular Ca2+ concentration, reversing the direction ofthe ciliary beat and swimming direction (15,16 (33), and hydrostatic pressure (34) have suggested that lipids also affect ion channel activity in Paramecium. In this report we now show that the functions ofvoltage-sensitive ion channels in the excitable membrane of Paramecium appear to be affected by a mutationally induced change in the phospholipid composition of the ciliary membrane. This mutant provides strong evidence that membrane lipids significantly influence the function of membrane proteins responsible for the generation of action potentials. METHODSCulture Conditions and Stocks. Cells were grown by routine methods (21, 35). H332PO4 was added to 0.5 /Ci/ml (1 Ci = 3.7 x 1010 becquerels) prior to addition of bacteria to the medium. In some cases stigmasterol (5 mg/liter) was also added to the medium prior to bacteria addition. The strains were: wild type, 51s; baA-i, d4-592; baA-2, d4-593; baA-3, d4-594; fna, d4-91; pwA, d4-94; baB, d5-599 (27).Cilia Isolation and Lipid Extraction. Cells in late logarithmic growth were harvested, washed extensively, and deciliated; the cilia were separated from bodies as described by Adoutte et al (25). Lipids were extracted...

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A mutant of Paramecium with increased relative resting potassium permeability

Cited by 34 publications

References 31 publications

Internal calcium concentration and potassium permeability in Paramecium

Internal calcium concentration and potassium permeability in Paramecium

Genetic dissection of attractant-induced conductances inParamecium

Mutational alteration of membrane phospholipid composition and voltage-sensitive ion channel function in paramecium.

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