volker endeward fabian itel samer al samir mohamed chami fredrik berg kristina hedfalk gerolf gros
Download
Skip this Video
Download Presentation
Intrinsic CO 2 permeability of cell membranes and role of CO 2 channels

Loading in 2 Seconds...

play fullscreen
1 / 31

Intrinsic CO 2 permeability of cell membranes and role of CO 2 channels - PowerPoint PPT Presentation


  • 147 Views
  • Uploaded on

Intrinsic CO 2 permeability of cell membranes and role of CO 2 channels. Volker Endeward, Fabian Itel, Samer Al-Samir, Mohamed Chami, Fredrik Öberg, Kristina Hedfalk, Gerolf Gros. Intrinsic CO 2 permeability of a red cell membrane. Gas permeability of synthetic phospholipid bilayers.

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about 'Intrinsic CO 2 permeability of cell membranes and role of CO 2 channels' - anthea


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
volker endeward fabian itel samer al samir mohamed chami fredrik berg kristina hedfalk gerolf gros
Intrinsic CO2 permeability of cell membranes and role of CO2 channels

Volker Endeward, Fabian Itel, Samer Al-Samir, Mohamed Chami, Fredrik Öberg,Kristina Hedfalk,Gerolf Gros

gas permeability of synthetic phospholipid bilayers
Gas permeability of synthetic phospholipid bilayers

Alberts et al.

Molecular Biology Of The Cell, 4th Edition

slide5
CO2

?

1. What are the intrinsic CO2 permeabilities of cell membranes?

  • Which mechanisms are responsible for the given intrinsic
  • permeabilities of cell membranes?
slide7
Mass spectrometer

H

16

O + C

18

O

16

O

2/

3

2

HC

18

O

16

O

-

+ H

+

2

1/

3

H

18

O

+ C

16

O

2

2

P

HCO3

-

P

H2O

P

CO2

H

18

O

+ C

16

O

1/3

2

2

H C

18

O

16

O

-

+ H

+

CA

2

2/3

H

16

O + C

18

O

16

O

2

Cell

slide11
PC:PS:Chol – vesicles with different cholesterol content

PC = Phosphatidylcholine

PS = Phosphatidylserine

Chol = Cholesterol (0 – 70%)

Ø = ~ 150 nm

slide12
70% chol.

[C18O16O] - [C18O16O]∞ (µM)

30% chol.

slide15
CO2 permeabilities of cell membranes appear to be essentially determined by their cholesterol content
slide16
cholesterol depletion

with β-cyclodextrin

cholesterol enrichment

with β-cyclodextrin

is cholesterol the cause of the low co 2 permeability of mdck cells
Is cholesterol the cause of the low CO2 permeability ofMDCK cells?

Reduction of cholesterol with cyclodextrin raises PCO2.

Enrichment with cholesterol lowers PCO2 compared to normal cells.

slide18
We show that cell membranes possess a low intrinsic CO2 permeability, often in the range of 0.01 cm/s.
  • This permeability is 2, and in one case 3, orders of magnitude lower than the CO2 permeability of pure artificial phospholipid bilayers.
  • The main cause of this low CO2 permeability is the cholesterol content of the cell membrane. With increasing cholesterol content PCO2 decreases
  • in artificial vesicles as well as in intact cells.
slide19
Physiological consequences of low CO2 membrane permeabilities

1. Consequences of the extremely low CO2 permeability of the

apical membrane of colon epithelium

2. Effect of low CO2 membrane permeability on red blood cell

gas exchange

slide20
PCO2 = 0.0015 cm/s

Consequences of low apical CO2 permeability in colonocytes

apical membrane

basal membrane

100

colon lumen

pCO

2

(

mmHg

)

capillary

40

20

0

diffusion pathway (µm)

slide22
From these considerations we can see that gas exchange of cells with
  • a low CO2 permeability is limited.
  • Hypothesis: cell membranes with normal cholesterol and low intrinsic PCO2 adapt their CO2 permeabilities to their needs by incorporating gas chanels in the membrane.
slide23
AQP1

AqpZ

aquaporin 1 as a co 2 channel in cholesterol containing lipid vesicles
Aquaporin 1 as a CO2 channel in cholesterol-containing lipid vesicles

PC:PS:Chol 8:2:10

Incorporation of AQP1 into vesicles causes a rise in PCO2

Change of PCO2 in vesicles with decreasing Lipid- Protein-Ratios (LPR)

aquaporin 1 as a co 2 channel in mdck cells
Aquaporin 1 as a CO2 channel in MDCK cells

Expression of AQP1 in MDCK cells raises PCO2

slide27
We conclude that in a membrane of normal cholesterol content and low CO2 permeability, incorporation of AQP1 into the membrane significantly increases the CO2 permeability in a concentration dependent manner.
  • AQP1 acts as a DIDS-sensitive CO2 channel.
summary
Summary

With rising cholesterol content the CO2 permeability ( PCO2) of lipid vesicles decreases drastically.

The intrinsic PCO2 of cell membranes is low due to their cholesterol content:

1) cell membranes and lipid vesicles with identical cholesterol content exhibit identical CO2 permeability

2) cholesterol-depleted cell membranes have an increased CO2 permeability, cholesterol-enriched cell membranes a reduced permeability

Cell membranes with normal cholesterol raise their CO2 permeability, when functionally required, by incorporation of CO2 channels:

1) AQP1 incorporated in lipid vesicles raises CO2 permeability in a concentration-dependent manner

2) AQP1 expression in MDCK cells increases membrane PCO2.

slide31
Medizinische Hochschule Hannover

Vegetative Physiologie

Samer Al-Samir

Timo Meine

Werner Zingel

Gerolf Gros

Universität BaselDept. Chemie / Biozentrum

Fabian Itel

Mohamed Chami

University of GothenburgDept. Chemistry/Biochemistry

Frederic Öberg

Kristina Hedfalk

ad