Mechanosignaling

How do focal adhesions disassemble?

Disassembly is critical during cell spreading and forward movement to allow FAs to extend outwards towards the cell periphery [1]. Disassembly of adhesions can take place as a result of retraction at the rear of the cell after adhesion maturation or at the base of protrusions during turnover. It is primarily mediated through tyrosine phosphorylation events and changes in cytoskeletal tension [2], which are controlled by regulators such as calpain [3] and microtubules [4].

Retraction-mediated disassembly is coordinated asymmetrically in order to support directional migration and usually occurs at the cell rear (reviewed in [5]). It is associated with “sliding” of the adhesions as the edge moves inwards [6]. The sliding movement seems to be Rho/myosin II-dependent, however, the mechanism is still unclear (reviewed in [7]). A study reporting differential regulation of the turnover rates of individual plaque proteins by mechanical force [8]. This indicates that their size and molecular composition change upon variation in stress and thus could initiate FA disassembly. Large protein aggregates are known to leave the adhesion complex and disperse as they move away from the adhesion site [9]. Clusters that disperse off the sliding adhesions have been observed to move centripetally along the cell’s lateral edges, coalesce with others and can be stable over 30 min before disintegrating [6].

Microtubules (MTs) are known to negatively regulate cell contractility and hence enhance disassembly (reviewed in [10]). They have been observed to target adhesion sites [11] and eventually cause sliding or destabilization of these structures relaxation of actin bundles at the end linked to adhesion foci [12]. MTs may stimulate this highly localized event either through the tyrosine kinase Arg, which inhibits Rho [13] or via the interplay of FAK-mediated destabilization and dynamin-driven /clathrin-mediated endocytosis of integrins [14][15] (reviewed in [5]). Kinesin is also implicated in MT-regulated focal delivery of components that retard adhesion growth and promote disassembly [16]. Evidence also exists for other mechanisms for MT-mediated disassembly where MT depolymerization promotes Rho-dependent contractility by releasing bound GEF, which may cause adhesion instability [17][18].

On the other hand, at the lamellipodium-lamellum interface, turnover of nascent adhesion structures occur during migration and is dependent on the forces generated by actin depolymerization and reorganization [19][20]. Turnover of these structures has an important role in maintaining a defined lamellipodium-lamellum boundary through the protrusion/contraction cycles and actin bundling in the lamellum [21].

FAK– Src signaling pathway seems to play critical role in mediating adhesion turnover at the cell front [22][23]. It is signaled through phosphorylation of Myosin light chain kinase (MLCK) by ERK/MAP kinase, which increases actomyosin contractility [24]. Under high force, high integrin density leads to less stable integrin-ECM adhesive bonds [25]. The resulting severing of actin linkages therefore releases the receptors [6][26]. Alternately, turnover can be enhanced by FAK-mediated transient suppression of Rho activity [27][28]. Proteolysis of key adhesion components such as talin [29], β3-integrin [30] and FAK [31] by calpain is also implicated in this function.

Recycling of individual integrins through active transport to the leading edge have been shown to resensitize integrins for ligand binding [32] (reviewed in [33]). Altogether, the coordinated disassembly, recycling, and directed transport thus maintain the balance of adhesions assembly and disassembly that is required for persistent migration.

References

1. Partridge MA, and Marcantonio EE. Initiation of attachment and generation of mature focal adhesions by integrin-containing filopodia in cell spreading. Mol. Biol. Cell 2006; 17(10):4237-48. [PMID: 16855018]
2. Crowley E, and Horwitz AF. Tyrosine phosphorylation and cytoskeletal tension regulate the release of fibroblast adhesions. J. Cell Biol. 1995; 131(2):525-37. [PMID: 7593176]
3. Franco SJ, and Huttenlocher A. Regulating cell migration: calpains make the cut. J. Cell. Sci. 2005; 118(Pt 17):3829-38. [PMID: 16129881]
4. Austin JH, and Carsen GM. Letter: Acute raumatic hematoma of aorta. J. Thorac. Cardiovasc. Surg. 1976; 71(2):321. [PMID: 1246156]
5. Broussard JA, Webb DJ, and Kaverina I. Asymmetric focal adhesion disassembly in motile cells. Curr. Opin. Cell Biol. 2008; 20(1):85-90. [PMID: 18083360]
6. Laukaitis CM, Webb DJ, Donais K, and Horwitz AF. Differential dynamics of alpha 5 integrin, paxillin, and alpha-actinin during formation and disassembly of adhesions in migrating cells. J. Cell Biol. 2001; 153(7):1427-40. [PMID: 11425873]
7. Parsons JT, Horwitz AR, and Schwartz MA. Cell adhesion: integrating cytoskeletal dynamics and cellular tension. Nat. Rev. Mol. Cell Biol. 2010; 11(9):633-43. [PMID: 20729930]
8. Wolfenson H, Bershadsky A, Henis YI, and Geiger B. Actomyosin-generated tension controls the molecular kinetics of focal adhesions. J. Cell. Sci. 2011; 124(Pt 9):1425-32. [PMID: 21486952]
9. Digman MA, Wiseman PW, Choi C, Horwitz AR, and Gratton E. Stoichiometry of molecular complexes at adhesions in living cells. Proc. Natl. Acad. Sci. U.S.A. 2009; 106(7):2170-5. [PMID: 19168634]
10. Small JV, Geiger B, Kaverina I, and Bershadsky A. How do microtubules guide migrating cells? Nat. Rev. Mol. Cell Biol. 2002; 3(12):957-64. [PMID: 12461561]
11. Kaverina I, Rottner K, and Small JV. Targeting, capture, and stabilization of microtubules at early focal adhesions. J. Cell Biol. 1998; 142(1):181-90. [PMID: 9660872]
12. Kaverina I, Krylyshkina O, and Small JV. Microtubule targeting of substrate contacts promotes their relaxation and dissociation. J. Cell Biol. 1999; 146(5):1033-44. [PMID: 10477757]
13. Peacock JG, Miller AL, Bradley WD, Rodriguez OC, Webb DJ, and Koleske AJ. The Abl-related gene tyrosine kinase acts through p190RhoGAP to inhibit actomyosin contractility and regulate focal adhesion dynamics upon adhesion to fibronectin. Mol. Biol. Cell 2007; 18(10):3860-72. [PMID: 17652459]
14. Ezratty EJ, Bertaux C, Marcantonio EE, and Gundersen GG. Clathrin mediates integrin endocytosis for focal adhesion disassembly in migrating cells. J. Cell Biol. 2009; 187(5):733-47. [PMID: 19951918]
15. Ezratty EJ, Partridge MA, and Gundersen GG. Microtubule-induced focal adhesion disassembly is mediated by dynamin and focal adhesion kinase. Nat. Cell Biol. 2005; 7(6):581-90. [PMID: 15895076]
16. Krylyshkina O, Kaverina I, Kranewitter W, Steffen W, Alonso MC, Cross RA, and Small JV. Modulation of substrate adhesion dynamics via microtubule targeting requires kinesin-1. J. Cell Biol. 2002; 156(2):349-59. [PMID: 11807097]
17. van Horck FP, Ahmadian MR, Haeusler LC, Moolenaar WH, and Kranenburg O. Characterization of p190RhoGEF, a RhoA-specific guanine nucleotide exchange factor that interacts with microtubules. J. Biol. Chem. 2000; 276(7):4948-56. [PMID: 11058585]
18. Krendel M, Zenke FT, and Bokoch GM. Nucleotide exchange factor GEF-H1 mediates cross-talk between microtubules and the actin cytoskeleton. Nat. Cell Biol. 2002; 4(4):294-301. [PMID: 11912491]
19. Alexandrova AY, Arnold K, Schaub S, Vasiliev JM, Meister J, Bershadsky AD, and Verkhovsky AB. Comparative dynamics of retrograde actin flow and focal adhesions: formation of nascent adhesions triggers transition from fast to slow flow. PLoS ONE 2008; 3(9):e3234. [PMID: 18800171]
20. Shemesh T, Verkhovsky AB, Svitkina TM, Bershadsky AD, and Kozlov MM. Role of focal adhesions and mechanical stresses in the formation and progression of the lamellipodium-lamellum interface [corrected]. Biophys. J. 2009; 97(5):1254-64. [PMID: 19720013]
21. Barthel W, and Markwardt F. Aggregation of blood platelets by adrenaline and its uptake. Biochem. Pharmacol. 1975; 24(20):1903-4. [PMID: 20]
22. Webb DJ, Donais K, Whitmore LA, Thomas SM, Turner CE, Parsons JT, and Horwitz AF. FAK-Src signalling through paxillin, ERK and MLCK regulates adhesion disassembly. Nat. Cell Biol. 2004; 6(2):154-61. [PMID: 14743221]
23. Owen KA, Pixley FJ, Thomas KS, Vicente-Manzanares M, Ray BJ, Horwitz AF, Parsons JT, Beggs HE, Stanley ER, and Bouton AH. Regulation of lamellipodial persistence, adhesion turnover, and motility in macrophages by focal adhesion kinase. J. Cell Biol. 2007; 179(6):1275-87. [PMID: 18070912]
24. Klemke RL, Cai S, Giannini AL, Gallagher PJ, de Lanerolle P, and Cheresh DA. Regulation of cell motility by mitogen-activated protein kinase. J. Cell Biol. 1997; 137(2):481-92. [PMID: 9128257]
25. Ballestrem C, Hinz B, Imhof BA, and Wehrle-Haller B. Marching at the front and dragging behind: differential alphaVbeta3-integrin turnover regulates focal adhesion behavior. J. Cell Biol. 2001; 155(7):1319-32. [PMID: 11756480]
26. Palecek SP, Huttenlocher A, Horwitz AF, and Lauffenburger DA. Physical and biochemical regulation of integrin release during rear detachment of migrating cells. J. Cell. Sci. 1998; 111 ( Pt 7):929-40. [PMID: 9490637]
27. Ren XD, Kiosses WB, Sieg DJ, Otey CA, Schlaepfer DD, and Schwartz MA. Focal adhesion kinase suppresses Rho activity to promote focal adhesion turnover. J. Cell. Sci. 2000; 113 ( Pt 20):3673-8. [PMID: 11017882]
28. Schober M, Raghavan S, Nikolova M, Polak L, Pasolli HA, Beggs HE, Reichardt LF, and Fuchs E. Focal adhesion kinase modulates tension signaling to control actin and focal adhesion dynamics. J. Cell Biol. 2007; 176(5):667-80. [PMID: 17325207]
29. Franco SJ, Rodgers MA, Perrin BJ, Han J, Bennin DA, Critchley DR, and Huttenlocher A. Calpain-mediated proteolysis of talin regulates adhesion dynamics. Nat. Cell Biol. 2004; 6(10):977-83. [PMID: 15448700]
30. Flevaris P, Stojanovic A, Gong H, Chishti A, Welch E, and Du X. A molecular switch that controls cell spreading and retraction. J. Cell Biol. 2007; 179(3):553-65. [PMID: 17967945]
31. Chan KT, Bennin DA, and Huttenlocher A. Regulation of adhesion dynamics by calpain-mediated proteolysis of focal adhesion kinase (FAK). J. Biol. Chem. 2010; 285(15):11418-26. [PMID: 20150423]
32. White DP, Caswell PT, and Norman JC. alpha v beta3 and alpha5beta1 integrin recycling pathways dictate downstream Rho kinase signaling to regulate persistent cell migration. J. Cell Biol. 2007; 177(3):515-25. [PMID: 17485491]
33. Puklin-Faucher E, and Sheetz MP. The mechanical integrin cycle. J. Cell. Sci. 2009; 122(Pt 2):179-86. [PMID: 19118210]