Faculty Opinions recommendation of Talin depletion reveals independence of initial cell spreading from integrin activation and traction.
Year: 2008
Type: peer-review
Abstract: Cell spreading, adhesion and remodelling of the extracellular matrix (eCM) involve bi-directional signalling and physical linkages between the eCM, integrins and the cell cytoskeleton [1][2][3] .the actinbinding proteins talin1 and 2 link ligand-bound integrins to the actin cytoskeleton and increase the affinity of integrin for the eCM 4-6 .Here we report that depletion of talin2 in talin1-null (talin1 -/-) cells did not affect the initiation of matrix-activated spreading or src family kinase (sFK) activation, but abolished the eCM-integrin-cytoskeleton linkage and sustained cell spreading and adhesion.specifically, focal adhesion assembly, focal adhesion kinase (FAK) signalling and traction force generation on substrates were severely affected.the talin1 head domain restored β1 integrin activation but only full-length talin1 restored the eCM-cytoskeleton linkage and normal cytoskeleton organization.Our results demonstrate three biochemically distinct steps in fibronectin-activated cell spreading and adhesion: 1) fibronectin-integrin binding and initiation of spreading, 2) fast cell spreading and 3) focal adhesion formation and substrate traction.We suggest that talin is not required for initial cell spreading.However, talin provides the important mechanical linkage between ligandbound integrins and the actin cytoskeleton required to catalyse focal adhesion-dependent pathways.Disruption of the talin1 gene in undifferentiated embryonic stem (ES) cells severely disrupts cell adhesion and cytoskeleton organization 7 .However, fibroblasts derived from talin1 -/-ES cells spread and adhere normally, presumably due to increased expression of the closely related talin2 (refs 7,8 ).To study the role of talin in initial cell responses to ECM signals, we constructed a mouse talin2 short interfering RNA (siRNA) expression plasmid and transfected it into the talin1 -/-fibroblasts.We observed that talin2 siRNA-expressing talin1 -/-cells began to round up in culture after 48 h.After 3.5 days, 77 ± 11% of the cells became rounded (mean ± s.d., n > 450, 3 repetitions), whereas most of the control siRNA-expressing cells showed an elongated morphology in culture.Co-transfection of a GFP-talin1 plasmid rescued the morphology change induced by talin2 siRNA (11 ± 3% and 15 ± 8% rounded up in control siRNA transfected and GFP-talin1 and talin2 siRNA co-transfected cells, respectively; mean 3Correspondence should be addressed to M.P.S.
Authors: Christopher Chen, Michele Wozniak
Institutions: Boston University, University of Pennsylvania
Language: English
Subfield: Immunology and Allergy
Field: Medicine
Domain: Health Sciences
Open Access status: green
OpenAlex ID: W4234609199