Description	Location	Protrusive Dimension	Actin Rearrangement	Lipids Involved	Microtubule Dependence	Pericellular Proteolysis	Duration of Structure
Lamellipodia137,138	Surface-attached, sheet-like protrusions	Leading edge of the cell	Width: 0.1 – 0.2 µm	Branched actin filaments	Yes PI(4,5)P2139	Induces lamellipodia extension140	Minimal141	Minutes142
Filopodia137,138	Finger-like projections	Usually located in regions of lamellipodia	Width: 0.1 – 0.3 µm Length: 3 –10 µm	Parallel actin filament bundles	Yes PI(4,5)P2, PI(3,4,5)P3	Regulates filopodia density in lamellipodia rich areas143	No	Minutes
Focal Adhesions144,145	Large clusters of transmembrane receptors, integrins, and cytosolic proteins that connect ECM and actin cytoskeleton	Leading edge of the cell	Width: 2 – 6 µm	Predominately parallel actin filament bundles but branched actin at end146	Yes PI(4,5)P2	Inhibition of microtubules leads to increased focal adhesions147	Minimal	Hours – depending on rate of cell migration
Podosomes6	Actin rich core that is surrounded by a ring of actin- associated and signaling proteins. Term applies to normal cells	Ventral cell surface Often clustered behind the leading edge of the cell	Width: 0.5 – 2 µm Length: > 2 µm	Branched and unbranched actin39	Yes PI(3,4,5)P3148	Required for elongation and/or formation 13,136	Yes MT1-MMP, uPAR13,149	Minutes
Invadopodia6,11	Actin rich core that is surrounded by a ring of actin- associated and signaling proteins. Term applies to normal cells	Ventral cell surface Often situated under the nucleus	Width: 0.5 – 2 µm Length: > 2 µm	Branched actin at the cell surface. Unbranched actin through the tip of the protrusion41	Yes PI(3,4)P2, PI(3)P, lipid rafts (Cav-1)29,92	Required for elongation but not formation41	Yes MMP2, MMP9, MT1-MMP, seprase, uPAR ADAMs 12, 15, 19,	Hours