Membrane Biosynthesis and Homeostasissfb1348.uni-muenster.de/sites/default/files/2019-01/Membrane...

Volker Gerke Institute of Medical Biochemistry

ZMBE

Center for Molecular Biology of Inflammation

Membrane Biosynthesis and

Homeostasis

Biological membranes

Biological membranes

Membrane lipids

Biosynthesis of membrane lipids

Biosynthesis of glycerophospholipids

Biosynthesis of glycerophospholipids

Biosynthesis of glycerophospholipids

Biosynthesis of glycerophospholipids

The bilayer transfer problem

Synthesis at cytosolic

leaflet

Regulated lipid translocation

Ceramide

Condensation

N-acylation H2O

FA

FA

H2O

Biosynthesis of sphingolipids

CDP-cholin

Sphingomyelin

UDP-activated sugars

Glycosphingolipids

Ceramide

Biosynthesis of sphingolipids

Biosynthesis of sphingolipids

Glycosphingolipids

Biosynthesis of cholesterol

Biosynthesis of cholesterol

Cholesterol incorporation into membranesConsequences: Lowers FA mobility

changes Tm of phase transition

Lowers membrane permeability for small molecules

Supports domain organization

Asymmetrical distribution of lipids

e.g. plasma membrane

Consequences:

Specific interactions

Signal transduction

Electric contribution to membrane potential

Biological membranes plasma membrane

PLCs

PLDs

Inositol and phosphatidylinositol metabolism

Generation of novel membrane binding sites

Generation of phosphatidic acid

Change in membrane potential

Generation of novel membrane binding sites

PLAs Generation of inflammatory mediators

Phospholipid degradation - signal transduction

Signal transducing lipids

Arachidonic acid

Inflammatory response

Prostaglandine

Signal transducing lipids - PLC action

PI(4,5)P2

Signal transducing lipids - PI kinases

Membrane microdomains (rafts)

Membrane microdomains rich in PIP2, cholesterol, sphingolipids Clustering of these microdomains into larger structures - signalling - membrane transport -  lipid driven

-  protein driven

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Model membranes

Giant unilamellar vesicles (GUV) – 1-100µm lipid composition and curvature chosen to mimick cellular membrane GUV prepared by electroformation between two Indium-tinoxide (ITO) covered slides 1h, T > Tm, lipid , 10Hz, rectangular wave, 1V (peak to peak)

POPC/DOPC/POPS/Chol/PIP2 (38.4:19.2:20:19.4:3)

Intercalating dyes showing a preference for Ld and Lo phases

DSPC/DOPC/Chol/NBD-DSPE (27:49.9:23:0.1)

GUV

Spontaneous lipid segregation Lo and Ld domains

Visualizing cholesterol – Model membranes

Alexa 594 – Cholesterol analogue

NBD-DSPE

Anna Livia Matos

PI(4,5)P2

PI(3,4,5)P3

Phosphoinositide segregation in cellular polarity

Membrane homeostasis Protein/membrane transport in eukaryontic cells

Principles of vesicle mediated transport

Vesicle tethering and transport

Membrane traffic along the secretory pathway

Membrane traffic along the secretory pathway

Membrane traffic along the endocytic pathway

Distribution of phosphoinositides among endocytic compartments

Domain organization in the endocytic pathway