Mechano-coupling and regulation of contractility
by the vinculin tail domain
Claudia Tanja Mierke 1*, Philip Kollmannsberger 1, Daniel Paranhos Zitterbart 1, James Smith 1, Ben Fabry 1 and Wolfgang Heinrich Goldmann 1
1 University of Erlangen-Nürnberg
* To whom correspondence should be addressed. E-mail: claudia.mierke{at}t-online.de.
Submitted on April 26, 2007
Revised on June 28, 2007
Accepted on 4 September 2007
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Abstract |
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Vinculin binds to multiple focal adhesion and cytoskeletal proteins and has been implicated in transmitting mechanical forces between the actin cytoskeleton and integrins or cadherins. It remains unclear to what extend the mechano-coupling function of vinculin also involves signaling mechanisms. We report the effect of vinculin and its head and tail domains on force transfer across cell adhesions and the generation of contractile forces. The creep modulus and the adhesion forces of F9 mouse embryonic carcinoma cells (wildtype), vinculin knock-out cells (vinculin -/-) and vinculin -/- cells expressing either the vinculin head domain, tail domain, or full-length vinculin (rescue) were measured using magnetic tweezers on fibronectin-coated super-paramagnetic beads. Forces of up to 10 nN were applied to the beads. Vinculin -/- cells and tail cells showed a slightly higher incidence of bead detachment at large forces. Compared to wildtype, cell stiffness was reduced in vinculin -/- and head cells and was restored in tail and rescue cells. In all cell lines, the cell stiffness increased by a factor of 1.3 for each doubling in force. The power-law exponent of the creep modulus was force-independent and did not differ between cell lines. Importantly, cell tractions due to contractile forces were suppressed markedly in vinculin -/- and head cells, whereas tail cells generated tractions similar to the wildtype and rescue cells. These data demonstrate that vinculin contributes to the mechanical stability under large external forces by regulating contractile stress generation. Furthermore, the regulatory function resides in the tail domain of vinculin containing the paxillin binding site.
Key Words:
actin dynamics, cytoskeleton, focal adhesions, magnetic tweezers, myosin, prestress
