Structure and regulation of insect plasma membrane H(+)V-ATPase

2000 ◽  
Vol 203 (1) ◽  
pp. 127-135 ◽  
Author(s):  
H. Wieczorek ◽  
G. Grber ◽  
W.R. Harvey ◽  
M. Huss ◽  
H. Merzendorfer ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Ion Transport ◽  
Manduca Sexta ◽  
Plasma Membranes ◽  
Transport Processes ◽  
Rich Source ◽  
Structural Studies ◽  
Transport Activity ◽  
Secondary Transport ◽  
General Aspects

H(+) V-ATPases (V-ATPases) are found in two principal locations, in endomembranes and in plasma membranes. The plasma membrane V-ATPase from the midgut of larval Manduca sexta is the sole energizer of all transepithelial secondary transport processes. At least two properties make the lepidopteran midgut a model tissue for studies of general aspects of V-ATPases. First, it is a rich source for purification of the enzyme and therefore for structural studies: 20 larvae provide up to 0.5 mg of holoenzyme, and soluble, cytosolic V(1) complexes can be obtained in even greater amounts of up to 2 mg. Second, midgut ion-tranport processes are strictly controlled by the regulation of the V-ATPase, which is the sole energizer of all ion transport in this epithelium. Recent advances in our understanding the structure of the V(1) and V(o) complexes and of the regulation of the enzyme's biosynthesis and ion-transport activity will be discussed.

Studies on the Epidermis of Temnocephala Vii.* The Basal Region, with Comments on 'Membrane Flow'

1985 ◽  
Vol 33 (4) ◽  
pp. 413 ◽  
Author(s):  
JB Williams
Keyword(s):  
Plasma Membrane ◽  
Ion Transport ◽  
Large Scale ◽  
Plasma Membranes ◽  
Basal Region ◽  
Ionic Regulation ◽  
Membrane Flow ◽  
Cytoplasmic Structures

Tubular infoldings of the plasmalemma, and other basal structures in the epidermis of Temnocephala novaezealandiae, are described. At times, the tubular invaginations are greatly elaborated, resulting in a considerably increased plasmalemmal area; also, complex lateral interdigitations occur at the boundaries of the differentiated syncytial epithelia. Many mitochondria are associated with the elaborated membrane. These modifications suggest an enhanced ion transport across the epidermis, and the epidermis is assumed to function in combination with the protonephridial tubules in ionic regulation. Other cytoplasmic structures are correlated with the enhanced plasma membrane, indicating possible pathways of membraneogenesis. Return to the normal epidermal cytomorphology evidently entails a large-scale disassembly of plasma membranes.

N-glycosylation controls functional activity of Oatp1, an organic anion transporter

2003 ◽  
Vol 285 (2) ◽  
pp. G371-G381 ◽  
Author(s):  
Thomas K. Lee ◽  
Albert S. Koh ◽  
Zhifeng Cui ◽  
Robert H. Pierce ◽  
Nazzareno Ballatori
Keyword(s):  
Plasma Membrane ◽  
Functional Activity ◽  
Plasma Membranes ◽  
Organic Anion ◽  
Xenopus Laevis Oocytes ◽  
Transport Activity ◽  
Anion Transporter ◽  
Glycosylation Sites ◽  
Quadruple Mutant ◽  
Taurocholate Transport

Rat Oatp1 (Slc21a1) is an organic anion-transporting polypeptide believed to be an anion exchanger. To characterize its mechanism of transport, Oatp1 was expressed in Saccharomyces cerevisiae under control of the GAL1 promoter. Protein was present at high levels in isolated S. cerevisiae secretory vesicles but had minimal posttranslational modifications and failed to exhibit taurocholate transport activity. Apparent molecular mass ( M) of Oatp1 in yeast was similar to that of unmodified protein, ∼62 kDa, whereas in liver plasma membranes Oatp1 has an M of ∼85 kDa. To assess whether underglycosylation of Oatp1 in yeast suppressed functional activity, Oatp1 was expressed in Xenopus laevis oocytes with and without tunicamycin, a glycosylation inhibitor. With tunicamycin, M of Oatp1 decreased from ∼72 to ∼62 kDa and transport activity was nearly abolished. Mutations to four predicted N-glycosylation sites on Oatp1 (Asn to Asp at positions 62, 124, 135, and 492) revealed a cumulative effect on function of Oatp1, leading to total loss of taurocholate transport activity when all glycosylation sites were removed. M of the quadruple mutant was ∼ 62 kDa, confirming that these asparagine residues are sites of glycosylation in Oatp1. Relatively little of the quadruple mutant was able to reach the plasma membrane, and most remained in unidentified intracellular compartments. In contrast, two of the triple mutants tested (N62/124/135D and N124/135/492D) were present in the plasma membrane fraction yet exhibited minimal transport activity. These results demonstrate that both membrane targeting and functional activity of Oatp1 are controlled by the extent of N-glycosylation.

Is there a Cl- pump?

1988 ◽  
Vol 255 (5) ◽  
pp. R677-R692
Author(s):  
G. A. Gerencser ◽  
J. F. White ◽  
D. Gradmann ◽  
S. L. Bonting
Keyword(s):  
Plasma Membrane ◽  
Atpase Activity ◽  
Membrane Fraction ◽  
Plasma Membranes ◽  
Direct Evidence ◽  
Objective Evaluation ◽  
Chemical Processes ◽  
Transport Processes ◽  
Cl Transport ◽  
Active Ion Transport

Three universally accepted mechanisms of Cl- transport across plasma membranes exist and they are 1) anion-coupled antiport, 2) cation-coupled symport, and 3) coupling to primary active ion transport through electrical and/or chemical processes. No unequivocal direct evidence has been provided for primary active Cl- transport (Cl- pump) despite numerous reports of cellular Cl- -stimulated adenosinetriphosphatase (ATPases) and of Cl- transport that cannot be accounted for by the three well-documented Cl- transport processes. It has been demonstrated that Cl- -stimulated ATPase activity is localized to both mitochondrial and microsomal aspects of the cellular apparatus. However, one group ascribes microsomal localization of Cl- -stimulated ATPase activity to mitochondrial contamination of that membrane fraction. Therefore, no Cl- pump could ever exist naturally in any plasma membrane. The other group simply states that there is plasma membrane localization of Cl- -stimulated ATPase activity that could function as a Cl- pump. Both arguments are logically advanced and their conclusions are consistent with their respective premises. Resolution to the question Is there a Cl- pump? rests with each reader's critique and objective evaluation.

scholarly journals Effects of Prolonged Washing on Primary and Secondary Transport Processes at the Plasma Membrane in Red Beet Storage Tissue

1997 ◽  
Vol 115 (1) ◽  
pp. 263-272 ◽  
Author(s):  
A. C. Marvier ◽  
L. E. Williams ◽  
R. A. Leigh ◽  
J. L. Hall
Keyword(s):  
Plasma Membrane ◽  
Transport Processes ◽  
Storage Tissue ◽  
Red Beet ◽  
Secondary Transport

scholarly journals Cell surface accessibility of GLUT4 glucose transporters in insulin-stimulated rat adipose cells. Modulation by isoprenaline and adenosine

1992 ◽  
Vol 288 (1) ◽  
pp. 325-330 ◽  
Author(s):  
S J Vannucci ◽  
H Nishimura ◽  
S Satoh ◽  
S W Cushman ◽  
G D Holman ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Cell Surface ◽  
Glucose Transport ◽  
Plasma Membranes ◽  
Glucose Transporter ◽  
Glucose Transporters ◽  
Transport Activity ◽  
Surface Accessibility ◽  
Adipose Cells ◽  
Membrane Concentration

Insulin-stimulated glucose transport activity in rat adipocytes is inhibited by isoprenaline and enhanced by adenosine. Both of these effects occur without corresponding changes in the subcellular distribution of the GLUT4 glucose transporter isoform. In this paper, we have utilized the impermeant, exofacial bis-mannose glucose transporter-specific photolabel, 2-N-4-(1-azi-2,2,2-trifluoroethyl)benzoyl-1,3-bis-(D-mannos- 4-yloxy)-2-propylamine (ATB-BMPA) [Clark & Holman (1990) Biochem. J. 269, 615-622], to examine the cell surface accessibility of GLUT4 glucose transporters under these conditions. Compared with cells treated with insulin alone, adenosine in the presence of insulin increased the accessibility of GLUT4 to the extracellular photolabel by approximately 25%, consistent with its enhancement of insulin-stimulated glucose transport activity; the plasma membrane concentration of GLUT4 as assessed by Western blotting was unchanged. Conversely, isoprenaline, in the absence of adenosine, promoted a time-dependent (t1/2 approximately 2 min) decrease in the accessibility of insulin-stimulated cell surface GLUT4 of > 50%, which directly correlated with the observed inhibition of transport activity; the plasma membrane concentration of GLUT4 decreased by 0-15%. Photolabelling the corresponding plasma membranes revealed that these alterations in the ability of the photolabel to bind to GLUT4 are transient, as the levels of both photolabel incorporation and plasma membrane glucose transport activity were consistent with the observed GLUT4 concentration. These data suggest that insulin-stimulated GLUT4 glucose transporters can exist in two distinct states within the adipocyte plasma membrane, one which is functional and accessible to extracellular substrate, and one which is non-functional and unable to bind extracellular substrate. These effects are only observed in the intact adipocyte and are not retained in plasma membranes isolated from these cells when analysed for their ability to transport glucose or bind photolabel.

scholarly journals Qualitative and quantitative comparison of glucose transport activity and glucose transporter concentration in plasma membranes from basal and insulin-stimulated rat adipose cells

1988 ◽  
Vol 249 (1) ◽  
pp. 155-161 ◽  
Author(s):  
H G Joost ◽  
T M Weber ◽  
S W Cushman
Keyword(s):  
Activation Energy ◽  
Plasma Membrane ◽  
Membrane Transport ◽  
Glucose Transport ◽  
Plasma Membranes ◽  
Glucose Transporter ◽  
Cytochalasin B ◽  
Transport Activity ◽  
Adipose Cells ◽  
Stimulation Of

Conditions are described which allow the isolation of rat adipose-cell plasma membranes retaining a large part of the stimulatory effect of insulin in intact cells. In these membranes, the magnitude of glucose-transport stimulation in response to insulin was compared with the concentration of transporters as measured with the cytochalasin-B-binding assay or by immunoblotting with an antiserum against the human erythrocyte glucose transporter. Further, the substrate- and temperature-dependencies of the basal and insulin-stimulated states were compared. Under carefully controlled homogenization conditions, insulin-treated adipose cells yielded plasma membranes with a glucose transport activity 10-15-fold higher than that in membranes from basal cells. Insulin increased the transport Vmax. (from 1,400 +/- 300 to 15,300 +/- 3,400 pmol/s per mg of protein; means +/- S.E.M.; assayed at 22 degrees C) without any significant change in Km (from 17.8 +/- 4.4 to 18.9 +/- 1.4 nM). Arrhenius plots of plasma-membrane transport exhibited a break at 21 degrees C, with a higher activation energy over the lower temperature range. The activation energy over the higher temperature range was significantly lower in membranes from basal than from insulin-stimulated cells [27.7 +/- 5.0 kJ/mol (6.6 +/- 1.2 kcal/mol) and 45.3 +/- 2.1 kJ/mol (10.8 +/- 0.5 kcal/mol) respectively], giving rise to a larger relative response to insulin when transport was assayed at 37 degrees C as compared with 22 degrees C. The stimulation of transport activity at 22 degrees C was fully accounted for by an increase in the concentration of transporters measured by cytochalasin B binding, if a 5% contamination of plasma membranes with low-density microsomes was assumed. However, this 10-fold stimulation of transport activity contrasted with an only 2-fold increase in transporter immunoreactivity in membranes from insulin-stimulated cells. These data suggest that, in addition to stimulating the translocation of glucose transporters to the plasma membrane, insulin appears to induce a structural or conformational change in the transporter, manifested in an altered activation energy for plasma-membrane transport and possibly in an altered immunoreactivity as assessed by Western blotting.

Ion transport in parasitic protozoa.

1992 ◽  
Vol 172 (1) ◽  
pp. 311-322
Author(s):  
T Bakker-Grunwald
Keyword(s):  
Plasma Membrane ◽  
Ion Transport ◽  
Life Cycles ◽  
Transport Processes ◽  
Ion Pumps ◽  
Secondary Active Transport ◽  
Parasitic Protozoa ◽  
Complex Life Cycles ◽  
Vacuolar Acidification ◽  
Endocytic Vesicles

Many parasitic protozoa go through complex life cycles in the course of which they adapt to widely different environments; ion transport processes are expected to play a role both in pathogenicity and in adaptation. So far, studies on ion transport have been virtually limited to Leishmania, Plasmodium and Entamoeba. The distribution of ion pumps in the former two organisms generally appears to conform to the picture established for other protozoa, i.e. a proton-motive P-ATPase in the plasma membrane provides the driving force for H(+)-coupled secondary-active transport, a proton-motive V-ATPase in the digestive vacuoles is responsible for vacuolar acidification, and an F-ATPase (ATP synthase) is found in the mitochondria. The situation in Entamoeba, an archaic organism that lacks mitochondria, could be different from that in the two other parasites in that a V-ATPase may be present and active both in the plasma membrane and in the membranes of the endocytic vesicles.

Iodide transport of thyroid plasma membranes

1981 ◽  
Vol 98 (2) ◽  
pp. 227-233 ◽  
Author(s):  
Y. Endo ◽  
H. Nakagawa ◽  
E. Aikawa ◽  
S. Ohtaki
Keyword(s):  
Plasma Membrane ◽  
Kinetic Study ◽  
Transport System ◽  
Plasma Membranes ◽  
External Medium ◽  
Membrane Vesicles ◽  
Monovalent Cations ◽  
Transport Activity ◽  
Iodide Concentration ◽  
Iodide Transport

Abstract. Plasma membranes consisting of closed vesicles were isolated from hog thyroid homogenate. The membrane vesicles showed uphill transport of iodide from an external medium containing monovalent cations, of which K+ induced iodide transport more potently than Na+. The activity of the iodide transport expressed as T/M[I−] was as little as 3 to 11 in the presence of K+, but was invariably present. The ratio reached a maximum within about 10 min and then decreased fairly rapidly to unity. The addition of SCN− or ClO−4 to the external medium inhibited iodide transport. The transport activity was found to be maximum at pH 7.0 to 7.5 in the external medium. A kinetic study showed that the transport rate was saturated with respect to the iodide concentration. These observations suggested the presence of a carrier-mediated iodide transport system which was coupled with K+ flux across the plasma membrane.

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