Emerging Concepts in Ion Channel Biophysics

Emerging Concepts in Ion Channel Biophysics

Poster Abstracts

1-POS

Board 1

Vinculin and Its Fundamental Role in Actin Bundling Formation

Ernesto Alva Sevilla

2,1

, Andrey Krokhotin

, Nikolay V. Dokholyan

University of Texas at San Antonio, San Antonio, TX, USA.

University of North Carolina at

Chapel Hill, Chapel Hill, NC, USA,

Vinculin is an abundant and essential cytoskeletal protein that localizes to focal adhesions and

adherent junctions. The interaction between vinculin and actin plays a pivotal role in linking

transmembrane receptors to the cytoskeleton, which in turn, is important for controlling cellular

force transmission, cell morphology and motility. Vinculin binds to F-actin and undergoes a

conformational change that induces formation of a cryptic dimer necessary for actin filament

bundling, but nature of the dimer formed remains unknown. Here, we employ computational

approaches, including discrete molecular dynamic simulations, to investigate actin-induced

conformational changes in the vinculin tail (Vt) domain that facilitate dimer formation and actin

bundling. We find that actin engagement with Vt alters both the N-terminal helix (H1) and C-

terminus of Vt, and that conformational changes within the N- and C-terminus are necessary for

the formation of stable interfaces with the actin surface. We argue that this interface is important

for Vt dimerization. We show that residue deletions with the C-terminus (∆CT1, ∆CT2, and

∆CT5) affect the stability of this interface, consistent with previously published experimental

findings that C-terminal deletions within Vt reduce actin bundling activity. These observations

are supported by additional mutagenesis data. Intriguingly, we find that the presence of

tryptophan at position 912 destabilizes H1 helix and postulate that instability introduced by

W912 plays an important role allowing H1 to unfold upon actin association. Experiments are in

progress to test our actin-induced vinculin dimer model and examine the role of this W912 in

vinculin-mediated actin bundling.