Cell Signaling and Migration
Erich Lidstone
April 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
Migration-promoting
event
Polarize, extend
protrusion
Transport necessary
proteins to
movement front
Adhere to ECM or TM
receptor proteins
Disassemble
adhesions
Move forward
over proteins
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
a4-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
•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
• a- and b- 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 AdhesionDependent 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