Cell adhesion - Integrin-mediated cell adhesion and migration

Integrin-mediated cell adhesion and migration

Cell migration is a coordinated process that involves rapid changes in the dynamics of actin filaments, together with the formation and disassembly of cell adhesion sites. External stimuli that control cell migration are transduced into intracellular biochemical signals through the interactions of transmembrane integrins that bind to the extracellular matrix (ECM) proteins [1].

Integrins are heterodimeric cell surface adhesion receptors formed by two noncovalently associated subunits, alpha and beta. There are 18 alpha and 8 beta subunits that associate to form 24 different heterodimers [2]. Most integrins recognize several ECM proteins, such as Laminin 1, Fibronectin and Collagen (types I, II and IV), whereas alpha-5/beta-1 integrin recognizes only Fibronectin [3].

The ECM, integrins and the cell cytoskeleton interact at sites called focal contacts [4]. The integrin-binding proteins Paxillin and Talin recruit Focal adhesion kinase (FAK1) and a cytoskeletal protein Vinculin to focal contacts. Alpha-actinin is a cytoskeletal protein that binds to Vinculin and crosslinks Actin in actomyosin stress fibers and tethers them to focal contacts. Phosphorylation of Alpha-actinin by FAK1 reduces the crosslinking of stress fibers and prevents maturation of the focal contacts [5]. Vinculin transiently recruits the Actin-related protein complex (Arp2/3) to new sites of integrin aggregation [6]. Arp2/3 complex nucleates new Actin filaments from the sides of preexisting filaments. This interaction requires phosphorylation of the Arp2/3 complex by p21-activated kinase 1 (PAK1) that leads to polymerization of Actin [7].

Zyxin is an Alpha-actinin and stress-fiber-binding protein found in mature contacts.

Activated Talin binds to Phosphatidylinositol-4,5-bisphosphate (PI(4,5)P2)-producing enzyme Phosphatidylinositol phosphate kinase type I gamma (PIPKI gamma) and activates it. PIPKI gamma also can be stimulated by tyrosine-protein kinase c-Src [8] and FAK1 phosphorylation [9]. PI(4,5)P2 enhances Talin association with Integrins and stimulates the direct transient interactions of diverse cytoskeleton actin-binding proteins Vinculin, Alpha-actinin and Wiskott-Aldrich syndrome-like (N-WASP), thereby regulating Actin polymerization by stimulating the actin-nucleating activity of the Arp2/3 complex [7], [10].

Integrin clustering promotes FAK1 autophosphorylation at Tyr397, thereby creating a binding site for c-Src. Phosphorylation of FAK1 at Tyr576 and Tyr577 mediated by c-Src maximizes catalytic activity of FAK1. Phosphorylation of FAK1 at Tyr925 mediated by c-Src creates a binding site for the Growth factor receptor-bound protein 2 (GRB2), thereby leading to the activation of the Extracellular signal-regulated kinase-1/2 (ERK1/2). The GRB2 binding can displace Paxillin from its binding sites on the FAK1, and Tyr925-phosphorylated FAK1 might be selectively released from the focal contacts.

ERK2 phosphorylates FAK1 at Ser910 and decreases Paxillin binding to FAK1. Within focal contacts, FAK1-c-Src-mediated phosphorylation of Paxillin promotes ERK2 binding. ERK2-mediated phosphorylation of Paxillin can facilitate FAK1 binding to Paxillin and enhance FAK1 activation. Thus, there might be a regulatory cycle in which c-Src- and ERK2-mediated phosphorylation of FAK1 promotes its release from focal contacts and ERK2-mediated phosphorylation of Paxillin promotes the association of non-phosphorylated FAK1 with Paxillin at new or growing focal contact sites [1]. Finally, local ERK2-mediated phosphorylation and activation of Myosin light chain kinase (MYLK1) together with inactivation of PAK1 contribute to cell-matrix adhesion dynamics [11].

Active FAK1-c-Src complex facilitates binding of the CRK-associated substrate (p130Cas) to FAK1 and its subsequent phosphorylation by c-Src. v-Crk sarcoma virus CT10 oncogene homolog (CRK) binds to phosphorylated p130Cas and facilitates activation of Ras-related C3 botulinum toxin substrate 1 (Rac1) by the Guanine nucleotide exchange factor Dock180 (DOCK1) [12]. Activation of Rac1 leads to membrane ruffles, formation of lamellipodia and cell migration [13].

Rac1 downstream effector PAK1 phosphorylates diverse target proteins, thereby leading to the activation of LIM-kinase 1 (LIMK1) [14], inhibition of Myosin light chain kinases (MLCK) [15], activation of Myosin regulatory light chains (MRLC) [16] and activation of the Arp2/3 complex [17].

FAK1 phosphorylates and activates the Ras protein-specific guanine nucleotide-releasing factor 1 (RASGRF1), an activator of Ras homolog gene family member A (RhoA) [18], whereas active c-Src in the complex with FAK1 phosphorylates and activates GTPase-activating protein Glucocorticoid receptor DNA binding factor 1 (p190RhoGAP), a RhoA inhibitory protein [19]. FAK1 thereby may regulate cytoskeletal dynamics by modulating activity of RASGRF1, p190RhoGAP, and their effector RhoA [1].

RhoA downstream Rho-associated kinases 1 and 2 (ROCK) directly phosphorylate LIM-kinase 2 (LIMK2). LIMK1 and LIMK2 phosphorylate actin-associated protein Cofilin. Cofilin exhibits actin-depolymerizing activity followed by reorganization of the Actin cytoskeleton [20], [21].

The activated ROCK kinases also phosphorylate and inactivate the Myosin light chain phosphatase (MLCP) [22] that attenuates phosphorylation of the Myosin light chains (MELC) and MRLC [23] and formation of actomyosin stress fibers.

References:

1. Mitra SK, Hanson DA, Schlaepfer DD
   Focal adhesion kinase: in command and control of cell motility. Nature reviews. Molecular cell biology 2005 Jan;6(1):56-68
2. Ruegg C, Dormond O, Mariotti A
   Endothelial cell integrins and COX-2: mediators and therapeutic targets of tumor angiogenesis. Biochimica et biophysica acta 2004 Mar 4;1654(1):51-67
3. Lee JW, Juliano R
   Mitogenic signal transduction by integrin- and growth factor receptor-mediated pathways. Molecules and cells 2004 Apr 30;17(2):188-202
4. Calderwood DA, Ginsberg MH
   Talin forges the links between integrins and actin. Nature cell biology 2003 Aug;5(8):694-7
5. Izaguirre G, Aguirre L, Hu YP, Lee HY, Schlaepfer DD, Aneskievich BJ, Haimovich B
   The cytoskeletal/non-muscle isoform of alpha-actinin is phosphorylated on its actin-binding domain by the focal adhesion kinase. The Journal of biological chemistry 2001 Aug 3;276(31):28676-85
6. DeMali KA, Barlow CA, Burridge K
   Recruitment of the Arp2/3 complex to vinculin: coupling membrane protrusion to matrix adhesion. The Journal of cell biology 2002 Dec 9;159(5):881-91
7. Dayel MJ, Mullins RD
   Activation of Arp2/3 complex: addition of the first subunit of the new filament by a WASP protein triggers rapid ATP hydrolysis on Arp2. PLoS biology 2004 Apr;2(4):E91
8. Lee SY, Voronov S, Letinic K, Nairn AC, Di Paolo G, De Camilli P
   Regulation of the interaction between PIPKI gamma and talin by proline-directed protein kinases. The Journal of cell biology 2005 Feb 28;168(5):789-99
9. Ling K, Doughman RL, Firestone AJ, Bunce MW, Anderson RA
   Type I gamma phosphatidylinositol phosphate kinase targets and regulates focal adhesions. Nature 2002 Nov 7;420(6911):89-93
10. Nayal A, Webb DJ, Horwitz AF
    Talin: an emerging focal point of adhesion dynamics. Current opinion in cell biology 2004 Feb;16(1):94-8
11. Danen EH, van Rheenen J, Franken W, Huveneers S, Sonneveld P, Jalink K, Sonnenberg A
    Integrins control motile strategy through a Rho-cofilin pathway. The Journal of cell biology 2005 May 9;169(3):515-26
12. Kiyokawa E, Hashimoto Y, Kobayashi S, Sugimura H, Kurata T, Matsuda M
    Activation of Rac1 by a Crk SH3-binding protein, DOCK180. Genes & development 1998 Nov 1;12(21):3331-6
13. Parsons JT, Martin KH, Slack JK, Taylor JM, Weed SA
    Focal adhesion kinase: a regulator of focal adhesion dynamics and cell movement. Oncogene 2000 Nov 20;19(49):5606-13
14. Edwards DC, Sanders LC, Bokoch GM, Gill GN
    Activation of LIM-kinase by Pak1 couples Rac/Cdc42 GTPase signalling to actin cytoskeletal dynamics. Nature cell biology 1999 Sep;1(5):253-9
15. Sanders LC, Matsumura F, Bokoch GM, de Lanerolle P
    Inhibition of myosin light chain kinase by p21-activated kinase. Science (New York, N.Y.) 1999 Mar 26;283(5410):2083-5
16. Sells MA, Boyd JT, Chernoff J
    p21-activated kinase 1 (Pak1) regulates cell motility in mammalian fibroblasts. The Journal of cell biology 1999 May 17;145(4):837-49
17. Vadlamudi RK, Li F, Barnes CJ, Bagheri-Yarmand R, Kumar R
    p41-Arc subunit of human Arp2/3 complex is a p21-activated kinase-1-interacting substrate. EMBO reports 2004 Feb;5(2):154-60
18. Zhai J, Lin H, Nie Z, Wu J, Ca?ete-Soler R, Schlaepfer WW, Schlaepfer DD
    Direct interaction of focal adhesion kinase with p190RhoGEF. The Journal of biological chemistry 2003 Jul 4;278(27):24865-73
19. Brouns MR, Matheson SF, Settleman J
    p190 RhoGAP is the principal Src substrate in brain and regulates axon outgrowth, guidance and fasciculation. Nature cell biology 2001 Apr;3(4):361-7
20. Wilson JG
    Reproduction and teratogenesis: current methods and suggested improvements. Journal - Association of Official Analytical Chemists 1975 Jul;58(4):657-67
21. Maekawa M, Ishizaki T, Boku S, Watanabe N, Fujita A, Iwamatsu A, Obinata T, Ohashi K, Mizuno K, Narumiya S
    Signaling from Rho to the actin cytoskeleton through protein kinases ROCK and LIM-kinase. Science (New York, N.Y.) 1999 Aug 6;285(5429):895-8
22. Riento K, Ridley AJ
    Rocks: multifunctional kinases in cell behaviour. Nature reviews. Molecular cell biology 2003 Jun;4(6):446-56
23. Pfitzer G
    Invited review: regulation of myosin phosphorylation in smooth muscle. Journal of applied physiology (Bethesda, Md. : 1985) 2001 Jul;91(1):497-503