Cell adhesion Adhesion molecule signaling Mechanotransduction Cell motility

Cell adhesion molecules Immunoglobulin-like Cadherin Integrin Selectin Dystroglycan

Integrins Alpha/Beta heterodimers Closed/Open/Ligated states Couple cytoskeletal and extracellular conformations Focal complex Insideout Ousidein Xiao et al., 2004

Integrin signaling Survival Focal Adhesion Kinase PTEN/SHP PI-3K Src/Grb2, Crk RhoGAP PTEN/SHP Phosphatase and tensin homolog on chromosome 10 PIP3->PIP2 PI-3K antagonist

Integrin signaling: motility Juliano 2002

Cadherins Cell-cell adhesion Catenin signaling Adherens junction Desmosome Catenin signaling p120 RhoGAP b Transcription factor a Cytoskeletal linker Differentiation/development Tissue aggregation Juliano 2002

Cadherin Signaling Cadherin/catenin signaling interacts with traditional growth factor receptors, incl wnt/frz/dsh and HGF/c-Met Juliano 2002

Immunoglobulin-like Ubiquitous class, CAM Several extracellular Ig like domains Not antibodies Short cytoplasmic tail Associates with ankyrin/ spectrin cytoskeleton MAP kinases Function Developmental guidance Immune cell response Juliano 2002

Mechanotransduction Mechanical conformational change Force Deformation Opposition of internal and external forces CAM-matrix adhesion CAM-cytoskeleton adhesion Deformability of series structures

Elastic Domains EGF Fibronectin (FN) Immunoglobulin (Ig) Complement like EGF Complement like Ig CN3D, UIUC Theoretical and computational biophysics group

Mechanical conformational changes Mechanical energy disrupts H-bonding Modular elasticity nm stretch 100%+ strain pN force Gao et al., 2002 PNAS

Cell growth-substrate interaction Substrate chemistry Ligand matching Integrin/CAM mediated differentiation Substrate mechanics Improved differentiation on elastic substrates Fewer stress fibers on softer materials Yeung et al 2005

Motility Motility vs. contraction Polymerization systems Actin Tubulin Filament – motor systems Actin-myosin Microtubule-kinesin/dynein

Structural reorganization Motion of focal adhesions (white) and surrounding gel (red) in corneal fibroblasts. Petroll et al 2003

Crawling Pseudopodia Actin filament dynamics Lammelapodia Filopodia Directional polymerization Treadmilling Photolabel actin monomers Cell moves relative to actin 2 minutes

Actin: polymerization dependent motion Disk shaped Adenine nucleotide binding ATPase activity Nucleotide exchange Promoted by Profilin Inhibited by Cofilin Filament formation Barbed/Pointed end Myosin S-1 “decoration” ADP maturation

Actin filament polymerization Asymmetric exchange of monomers Myosin fragment

Filament regulation Exchange proteins Monomer recycling Profilin PROmotes filament growth towards barb Nucleotide exchange factor Cofilin ADP-Actin binding Filament repair Monomer recycling Cofilin disassembles ADP-actin Profilin regenerates ATP-actin

Monomer recycling Facilitates “treadmilling” Membrane extension Profilin carries ATP-actin to leading edge ATP-ADP conversion as filament matures Cofilin disassembles ADP-actin

Rho family GTPases GTP dependent cofactors, like Ga subunits Rho Kinase, mDia, Components of shape-dependent processes Motility, cell cycle, phagocytosis Heasman & Ridley 2008

Rho family GTPases Rho Rac cdc42 Stress fibers, integrin, selectin Lamellipodia, growth factors cdc42 Filopodia, cytokines Constitutively active cdc42 Rac Rho Normal cell

Rho family signaling diversity cdc42 Rac Rho WASP IRSp53 mDia2 PAK WAVE mDia2 PAK RhoK LIMK LIMK ARP2/3 ARP2/3 formin MLCK MLP coflin coflin myosin Actin branching Actin polymerization Actin turnover Actin polymerization Actin turnover Lamellipodia Stress fiber Filopodia Filopodia

Microtubule Regular array of a/b dimers Spontaneous tube formation Polar

Motor Proteins Myosin-actin Kinesin-tubulin Dynein-tubulin

Motor step cycle One head Two head “Hand-over-hand”

Motor step systems Myosin Kinesin AM AMT AMDP AMD MT MDP M MD T P D Shape Changes “Weak” Binding “Strong” Myosin T P D MtK1 MtK1T MtK1DP MtK1DK2 MtK2 Kinesin P K1 K1T MtK1DPK2D MtK1DPK2 Mt “Weak” Binding K2 “Strong” Binding K2 Shape Changes T

Kinesin/Dynein motility Vesicular transport Kinesin Toward + Away from nucleus Dynein Toward – Toward Nuc 0.1-1 um/s

Myosin motility Cytoplasmic streaming (plants) Muscle Transport of ER along actin tracks 60 um/s Muscle Specialized bipolar myosin filaments Opposing motion in adjacent actin filaments 1-10 um/s

Highly ordered filaments Crystalline polymerization facilitates molecular interaction Maximize density of force generating elements Double-headed Myosin “J” structure on filament surface Woodhead et al 2005

Regulation of force (smooth muscle) Thick filament regulation Regulatory myosin light chain phos Myosin light chain kinase (MLCK) Calmodulin Slow, sustained

Regulation of force (striated muscle) Thin filament regulation Steric availability of actin Tropomyosin Troponin I,C,T Cooperative Rapid Weak myosin binding Strong myosin binding Actin Tropomyosin