Model systems for studying cell adhesion and biomimetic actin networks

Abstract

SummaryMany cellular processes, such as migration, proliferation, wound healing and tumor progression are based on cell adhesion. Amongst different cell adhesion molecules, the integrin receptors play a very significant role. Over the past decades the function and signalling of various such integrins have been studied by incorporating the proteins into lipid membranes. These proteolipid structures lay the foundation for the development of artificial cells, which are able to adhere to substrates. To build biomimetic models for studying cell shape and spreading, actin networks can be incorporated into lipid vesicles, too. We here review the mechanisms of integrin-mediated cell adhesion and recent advances in the field of minimal cells towards synthetic adhesion. We focus on reconstituting integrins into lipid structures for mimicking cell adhesion and on the incorporation of actin networks and talin into model cells.

Synthetische Adhäsion von Integrin‐Liposomen als minimales Zellmodell

“…In den letzten Jahren wurden unterschiedliche Proteine des fokalen Adhäsionskomplexes in Lipidvesikel eingebaut, um damit die molekulare Beschaffenheit der Zelladhäsion biophysikalisch und biochemisch zu erklären 5. Im Einzelnen wurde Integrin α IIb β 3 aus Blutplättchen in kleinen Liposomen mithilfe der Detergens‐Dialyse‐Methode rekonstituiert 6.…”

Minimal Synthetic Cells to Study Integrin‐Mediated Adhesion

“…[5] In particular, the integrin α IIb β 3 from blood platelets was reconstituted into small liposomes using a detergent dialysis method. [6] The biological activity of the reconstituted integrin α IIb β 3 was confirmed by fibrinogen (Fg) binding assays.…”

Reconstituting the actin cytoskeleton at or near surfaces in vitro

“…All images Léa Trichet, 2004-2005. The main characteristics include 1) the system has a cell-like geometry confined by a lipid bilayer to mimic the cell membrane, 2) actin filament nucleation occurs at the membrane by physiological factors such as the Arp2/3 complex or another nucleator such as formin, 3) attachment to the membrane is ensured by transient links via the Arp2/3 complex and physiological actin filament-membrane linkers such as ezrin, 4) non-muscle myosins are included in the artificial cell interior, 5) actin filaments disassemble either due to the activity of proteins such as ADF/cofilin or to the buckling/severing action that results from myosin contraction and 6) the actin monomers thus liberated are recycled to the cell membrane for subsequent rounds of nucleation. Like in cells, spontaneous formation of filaments in the "cell" interior is inhibited by maintaining free actin in its profilin-bound form.…”

“…This review will be about the progress over the last 15 years in the field of reconstitution of dynamic actin and acto-myosin networks at surfaces or under confinement, and how technological advances have been used to further our understanding of cellular actin dynamics. Other excellent reviews on reconstitution have been published over the last 5 years concentrating on actin and adhesion, membrane-bound actin and single filament dynamics [3][4][5][6][7]. The focus here is actin and acto-myosin networks at or near surfaces in vitro, to mimic cellular confinement and geometry.…”