関: lamellipodia、lobopodia、lobopodium

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出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2014/05/07 08:24:04」(JST)

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The lamellipodium (plural lamellipodia) (from Latin "Lamina" - thin sheet, "pod" - foot) is a cytoskeletal protein actin projection on the mobile edge of the cell. It contains a quasi-two-dimensional actin mesh; the whole structure propels the cell across a substrate (Alberts, et al., 2002). Within the lamellipodia are ribs of actin called microspikes, which, when they spread beyond the lamellipodium frontier, are called filopodia (Small, et al., 2002). The lamellipodium is born of actin nucleation in the plasma membrane of the cell (Alberts, et al., 2002) and is the primary area of actin incorporation or microfilament formation of the cell.

Description

Lamellipodia are found primarily in very mobile cells, for example the keratinocytes of fish and frogs, which are involved in the quick repair of wounds, crawling at a speeds of 10-20μm/minute over epithelial surfaces. A lamellipodium separated from the main part of a cell by scratching across the cell with a pipette tip can continue to crawl freely about on its own.

Lamellipodia are a characteristic feature at the front, leading edge, of motile cells. They are believed to be the actual motor which pulls the cell forward during the process of cell migration. The tip of the lamellipodium is the site where exocytosis occurs in migrating mammalian cells as part of their clathrin-mediated endocytic cycle. This, together with actin-polymerisation there, helps extend the lamella forward and thus advance the cell's front. It thus acts as a steering device for cells in the process of chemotaxis. It is also the site from which particles or aggregates attached to the cell surface migrate in a process known as cap formation.

Structure

Structurally, the barbed ends of the microfilaments (localized actin monomers in an ATP-bound form) face the "seeking" edge of the cell, while the pointed ends (localized actin monomers in an ADP-bound form) face the lamella behind (Cramer, 1997). This creates treadmilling throughout the lamellipodium, which aids in the retrograde flow of particles throughout (ibid.). Arp2/3 complexes are present at microfilament-microfilament junctions in lamellipodia, and help create the actin meshwork. Arp 2/3 can only join onto previously existing microfilaments, but once bound it creates a site for the extension of new microfilaments, which creates branching (Weed, et al., 2000). Another molecule that is often found in polymerizing actin with Arp2/3 is cortactin, which appears to link tyrosine kinase signalling to cytoskeletal reorganization in the lamellipodium and its associated structures (ibid.).

Rac and Cdc42 are two Rho-family GTPases which are normally cytosolic but can also be found in the cell membrane under certain conditions (Small, et al., 2002). When Cdc42 is activated, it can interact with Wiskott-Aldrich syndrome protein (WASp) family receptors, in particular N-WASp, which then activates Arp2/3. This stimulates actin branching and increases cell motility (Small, et al., 2002). Rac1 induces cortactin to localize to the cell membrane, where it simultaneously binds F-actin and Arp2/3. The result is a structural reorganization of the lamellipodium and ensuing cell motility (Weed, et al., 2000). Rac promotes lamellipodia while cdc42 promotes filopodia (Hall 1998).

Ena/VASP proteins are found at the leading edge of lamellipodia, where they promote actin polymerization necessary for lamellipodial protrusion and chemotaxis. Further, Ena/VASP prevents the action of capping protein, which halts actin polymerization. (Bear and Gertler, 2009)

References

Alberts, Bruce, et al. Molecular Biology of the Cell. Fourth Edition. Garland Science, Taylor & Francis Group. New York, 2002: pgs 908, 931, 973-975.
Hall A, 1998. Science 279:509
Cramer, Louise P. Molecular Mechanism of Actin-Dependent retrograde Flow in Lamellipodia of Motile Cells. Frontiers in Bioscience, 2, d260-270, June 1, 1997.
Small, J. Victor, et al. The lamellipodium: where motility begins. Trends in Cell Biology, Vol. 12 No. 3, March 2002: pgs. 112-120.
Weed, Scott A., et al. Cortactin Localization to Sites of Actin Assembly in Lamellipodia Requires Interactions with F-Actin and the Arp2/3 Complex. The Journal of Cell Biology, Vol.151 No.1, October 2, 2000. pgs 29-40. Available Online
Bear and Gertler. J Cell Sci. 2009 Jun 15;122(Pt 12):1947-53.
Video tour of cell motility

External links

MBInfo - Lamellipodia
MBInfo - Lamellipodia Assembly

English Journal

The effect of sibutramine on platelet morphology of Spraque-Dawley rats fed a high energy diet.

Oberholzer HM, Van Der Schoor C, Pretorius E.SourceDepartment of Anatomy, Faculty of Health Sciences, University of Pretoria, South Africa.
Microscopy research and technique.Microsc Res Tech.2013 Jun;76(6):653-7. doi: 10.1002/jemt.22214. Epub 2013 Apr 11.
The aim of this study was to investigate the effect of Sibutramine on platelet ultrastructure and discuss the morphological observations in relation to known physiological effects of the compound. Six-week-old, female Spraque-Dawley rats were used in this study. The animals were placed on a high ene
PMID 23576325

CIP4 Controls CCL19-Driven Cell Steering and Chemotaxis in Chronic Lymphocytic Leukemia.

Malet-Engra G, Viaud J, Ysebaert L, Farcé M, Lafouresse F, Laurent G, Gaits-Iacovoni F, Scita G, Dupré L.SourceAuthors' Affiliations: Institut National de la Santé et de la Recherche Médicale (INSERM), U1043, Centre de Physiopathologie de Toulouse Purpan; INSERM, U1048; INSERM, U1037, Centre de Recherche en Cancérologie de Toulouse; Centre National de la Recherche Scientifique (CNRS), U5282; Université Toulouse III Paul-Sabatier; Department of Hematology, Purpan University Hospital, Toulouse, France; IFOM (FIRC Institute for Molecular Oncology); and Dipartimento di Scienze della Salute, Università degli Studi di Milano, Milan, Italy.
Cancer research.Cancer Res.2013 May 21. [Epub ahead of print]
Solid tumor dissemination relies on the reprogramming of molecular pathways controlling chemotaxis. Whether the motility of nonsolid tumors such as leukemia depends on the deregulated expression of molecules decoding chemotactic signals remains an open question. We identify here the membrane remodel
PMID 23644527

Hematopoietic progenitor kinase 1 (HPK1) is required for LFA-1-mediated neutrophil recruitment during the acute inflammatory response.

Jakob SM, Pick R, Brechtefeld D, Nussbaum C, Kiefer F, Sperandio M, Walzog B.SourceWalter Brendel Centre of Experimental Medicine, Ludwig-Maximilians-Universität, Munich, Germany; and.
Blood.Blood.2013 May 16;121(20):4184-94. doi: 10.1182/blood-2012-08-451385. Epub 2013 Mar 4.
Recruitment of polymorphonuclear neutrophils (PMNs) to sites of acute inflammation critically depends on β2 integrins (CD11/CD18). Recently, the mammalian actin-binding protein 1 (mAbp1) was identified as an important adaptor protein regulating PMN trafficking downstream of β2 integrins. Here, we
PMID 23460610

Japanese Journal

せん断応力に依存した血管内皮細胞の3次元ネットワーク形成(流体工学,流体機械)

阿部順紀,須藤亮,池田満里子,谷下一夫
日本機械学會論文集. B編 76(767), 1061-1067, 2010-07-25
The mechanical stimulus of shear stress enhances the function of endothelial cells as well as their microvessel network formation. Using an in vitro three-dimensional (3-D) model set in a parallel-pla …
NAID 110007682120

Inhibition of endothelial cell chemotaxis toward FGF-2 by gefitinib associates with downregulation of Fes activity

Kanda Shigeru,Naba Alexandra,Miyata Yasuyoshi
International Journal of Oncology 35(6), 1305-1312, 2009-12
… Gefitinib inhibited lamellipodium formation by endothelial cells induced by FGF-2, but not by VEGF-A. … Taken together, these results indicate that FGF-2 activates Fes via the second CCD, leading to lamellipodium formation and chemotaxis by endothelial cells, and gefitinib may act through Fes as an inhibitor of FGF-2-driven angiogenesis. …
NAID 120002693650