MEMBRANE SHAPING AND REMODELING BY PROTEINS THANKS AND CREDIT: FELIX CAMPELO HARVEY MCMAHON ADI PICK TEL AVIV GROUP: COLLABORATION: TOM SHEMESHLEONID CHERNOMORDIK WINFRIED WEISSENHORNGUR FABRIKANT TOM RAPOPORT

h/R~ 0.2 Radius of curvature R ~ 20 nm is close to the monolayer thickness h ~ 4 nm INTRACELLULAR MEMBRANE SHAPES AND DYNAMICS VIRAL MEMBRANE DYNAMICS

THREE ESSENTIALLY DIFFERENT GEOMETRICAL TRANSFORMATIONS MEDIATING DYNAMIC SHAPING BENDING (GENERATION OF CURVATURE) REMODELING BY FISSION OR FUSION (CHANGE OF MEMBRANE CONTINUITY, AND MEMBRANE TOPOLOGY ) FISSION FUSION

MEMBRANES RESISTS TO BOTH BENDING AND REMODELING MEANING THAT ENERGY HAS TO BE SUPPLIED BY SPECIAL PROTEINS

MEMBRANE RESISTENCE TO MEAN CURVATURE GENERATION: INVOLVED IN SHAPING AND REMODELING POSITIVE CURVATURE NEGATIVE CURVATURE BENDING STRESS BENDING ENERGY: HELFRICH MODEL BENDING (SPLAY) MODULUS SPONTANEOUS CURVATURE

ENERGY OF GAUSSIAN CURVATURE (HELFRICH MODEL) CHANGE OF MEMBRANE CONNECTIVITY (TOPOLOGY): INVOLVED IN REMODELNG CONSIDERABLE ENERGY IS ASSOCIATED WITH THE FISSION EVENT MODULUS OF GAUSSIAN CURVATURE IN ADDITION, TRANSIENT MEMBRANE DISCONTINUITY REQUIRES ENERGY

QUESTIONS TO ANSWER: PHYSICS: MECHANISTIC PRINCIPLES OF MEMBRANE BENDING AND FUSION/FISSION BY DIFFERENT PROTEINS BASED ON ENERGY CALCULATIONS. BIOLOGY: WHETHER THESE PRINCIPLES ARE UNIVERSAL AND DETERMINE ACTION OF DIVERSE PROTEINS BIOLOGY: WHETHER SAME PROTEINS CAN DRIVE BOTH FUSION AND FISSION BIOLOGY: WHETHER SAME PROTEINS CAN BE USED TO DRIVE MEMBRANE BENDING AND REMODELING OR DIFFERENT PROTEINS ARE NEEDED

CURVATURE GENERATION BY LIPIDS EFFICTIVE NON-BILAYER SHAPES OF LIPID MOLECULES ASYMMETRY OF TWO MONOLAYERS: a.DIFFERENT NUMBERS OF LIPID MOLECULES b.DIFFERENT LIPID COMPOSITIONS FOR BILAYER ASYMMETRICAL STRUCTURE OF LIPID MOLECULES FOR MONOLAYER

SPONTANEOUS CURVATURES OF REPRESENTATIVE LIPIDS (RAND AND FULLER) X-rays measurements of lipid mesophases P Rand (Brock Univ., Canada) Lysophosphatidylcholine (LPC): Common Lipids: Phosphatidylcholine (PC): Lysolipids: Hexagonal lipids DioleoylPE (DOPE) Diacylglycerol (DAG)

MECHANISMS OF MEMBRANE CURVATURE GENERATION BY DIRECT ACTION OF PROTEINS HYDROPHOBIC INSERTIONSCAFFOLDING CAMPELO ET AL 2008 VOTH ET AL 2008

SYNAPTOTAGMIN (D.Z.HERRICK ET AL., 2006) FUSION PEPTIDES AMPHIPATHIC HELICES C2 DOMAINS L. TAMM, BBA 2007 HYDROPHOBIC-INSERTION MECHANISM OF MEMBRANE BENDING N-BAR DOMAINS SMALL G-PROTEINS

STRUCTURE MODEL OF ACTION HYDROPHOBIC INSERTION PROTEINS: EPSIN TUBULATION OF PIP2 BILAYERS D=20nm

SCAFFOLDING PROTEINS: BAR DOMAIN PROTEINS Endophilin BAR N-BAR STRUCTURE MODEL OF ACTION TUBULATION OF PS BILAYERS D=20nm

STRUCTURE EHD2 MODEL OF ACTION TUBULATION IN VIVO BY OVEREXPRESSION OTHER TYPE OF SCAFFOLDING PROTEINS. EPSIN HOMOLOGY DOMAINS TUBULATION OF PS BILAYERS D=20nm

SMALL INCLUSION GENERATES ELASTIC DEFORMATION OF THE MONOLAYER MATRIX SMALL HYDROPHOBIC INSERTION MECHANISM: QUALITATIVELY

MEMBRANE AS A THICK LAYER: RELEVANT SCALES ARE COMPARABLE WITH MEMBRANE THICKNESS INTRA-MEMBRANE DISTRIBUTION OF STRESSES AND RIGITIES from Illya, Lipowsky and Shillcock, J Chem Phys 122, (2005) σ TRANS-MEMBRANE STRESS PROFILE

TRANS-MEMBRANE ELASTICITY PROFILE λTλT STRETCHINGTRANSVERSE SHEAR λSλS λTλT λSλS λ

COMPUTING MEMBRANE BENDING BY INSERTIONS BEFORE INSERTION DEFORMED STATE AFTER INSERTION LOOKING FOR CONFORMATION OF MINIMAL ELASTIC ENERGY FELIX CAMPELO

EFFECTIVE SPONTANEOUS CURVATURE OF INSERTION Z inc /h MAXIMAL SPONT.CURV. FOR INCLUSION ζ inc h ~ 0.75 MAXIMAL SPONT.CURV. FOR LIPID (LPC) ζ LPC h ~ 0.3 EFFECTIVE SPONTANEOUS CURVATURE OF INSERTION

0.05 z inc h MEMBRANE TUBULATION BY N-BAR DOMAIN

SHALLOW HYDROPHOBIC INSERTIONS ARE MORE EFFECTIVE THEN LIPIDS IN CURVATURE GENERATION

CURVATURE GENERATION BY SCAFFOLDING PROTEINS: SHAPING OF ENDOPLASMIC RETICULUM