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Cell Signaling and Migration
Erich LidstoneApril 29, 2009
Cell Signaling and Migration
• Importance of cell migration• Major steps of migration• Signaling pathways• Lipid rafts• Adhesion-dependent trafficking
Importance of Cell Migration
• Embryonic development• Chemotaxis• Tissue turnover• Wound healing• Immunity
Cell Migration and the Immune Response
• http://www.youtube.com/watch?v=MgVPLNu_S-w
Importance of Cell Migration
• Pathological processes– Vascular disease– Osteoporosis
• Chronic inflammatory diseases– Rheumatoid arthritis– Multiple sclerosis– Cancer– Mental retardation
Cell Migration Cycle
Polarize, extend protrusion
Migration-promoting event
Adhere to ECM or TM receptor proteins
Move forward over proteins
Disassemble adhesions
Transport necessary proteins to
movement front
Microtubule dynamics promote efficient exploration of the peripheral cytoplasmic domain of a neuronal growth cone. An example of a single dynamically unstable microtubule undergoing assembly followed by disassembly (bottom). Microtubule behavior integrated over 10 minutes in the peripheral growth cone lamellipodium (top).
Forscher Lab, Yale, Department of Molecular, Cellular, and Developmental Biology
Actin Polymerization• FAST-growing “barbed” end• SLOW-growing “pointed” end
• Lamellipodia – branching dendritic network configuration
• Filipodia – long parallel bundles of filaments
• Mediated by Arp2/3 complex• Causes branching of existing
filaments
Movement
• Leading edge moves by “Brownian ratchet”• Uses thermal energy built up by deforming
existing filaments• Does not derive energy directly from actin
polymerization
Cell migration detection
• Akt/PKB-GFP fusion• 4-integrin staining• PTEN-GFP fusion• FRET of GFP-V12Rac
with an effector molecule
Cell Migration Effectors•Profilin•Thymosin•Cofilin•Capping proteins•Cortactin stabilizes branches•Cross-linkers•filamin A•-actinin
Cell Polarization
•Polarity intrinsic to migrating cell•Vesicle trafficking toward the leading edge•Localization of the MTOC and golgi apparatus•PTEN resides at cell margins•PI3K resides at the leading edge•PIP3 production at the leading edge
Protrusion and Adhesion Formation
Integrins and Adhesion in Migration
• Integrins support adhesion to ECM or neighboring cells• Activate migration-related signaling molecules• - and - subunits interact with signaling proteins ,
undergo conformational changes• Integrin clustering• Downstream intracellular signaling– Tyrosine phosphorylation– GTPase activation– Phospholipid biosynthesis– Adhesion complex integrity
Tractional Forces
• Integrins also function as sites of traction• Cell uses them as a substrate over which it
moves during migration• Balance between adhesion at the leading edge
and disassembly at the trailing edge• Junction density• Rate of disassembly
Adhesion Disassembly
• Important at both the front and the rear of the cell
• Front – junctions disassembled as new ones are assembled in the formation of the protrusion
• Rear – junctions must be disassembled to provide materials and release cell from rear direction
Cell Migration Summary
• Migration is promoted• Cell undergoes polarization• Leading edge reconfigures junctions, actin
filaments, and microtubules• Trailing edge undergoes junction disassembly• Cell uses integrins for a combination of
traction and intracellular signaling• Cell reevaluates direction of migration
Arf6 and Microtubules in Adhesion-Dependent Trafficking of Lipid Rafts
• Detailed analysis of adhesion modulation• Lipid raft movement• Cell movement
Cytoskeletal Regulation of Raft Endocytosis
Identification of the Intracellular Compartment
Identification of the Intracellular Compartment
Role of Arf6 in Raft Trafficking
Role of Arf6 in Raft Trafficking
Role of Arf6 in Raft Trafficking
Inhibition of Arf6 Function
Inhibition of Arf6 Function
Adhesion-dependent Activation of Arf6 Promotes Raft Exocytosis
Adhesion-dependent Activation of Arf6 Promotes Raft Exocytosis
Microtubules in Raft Exocytosis
Lipid Raft Trafficking Summary
References