Nanomechanical Properties of Artificial Lipid Bilayers Composed of Fluid and Polymerizable Lipids

When nuclear membranes are stretched, the peripheral membrane enzyme cytosolic phospholipase A2 (cPLA2) binds via its calcium-dependent C2 domain (cPLA2-C2) and initiates bioactive lipid signaling and tissue inflammation. More than 150 C2-like domains are encoded in vertebrate genomes. How many of them are mechanosensors and quantitative relationships between tension and membrane recruitment remain unexplored, leaving a knowledge gap in the mechanotransduction field. In this study, we imaged the mechanosensitive adsorption of cPLA2 and its C2 domain to nuclear membranes and artificial lipid bilayers, comparing it to related C2-like motifs. Stretch increased the Ca2+ sensitivity of all tested domains, promoting half-maximal binding of cPLA2 at cytoplasmic resting-Ca2+ concentrations. cPLA2-C2 bound up to 50 times tighter to stretched than to unstretched membranes. Our data suggest that a synergy of mechanosensitive Ca2+ interactions and deep, hydrophobic membrane insertion enables cPLA2-C2 to detect stretched membranes with antibody-like affinity, providing a quantitative basis for understanding mechanotransduction by C2-like domains.

Download Full-text

Functional reconstitution of receptors in artificial lipid bilayers

Neuroscience Letters ◽

10.1016/0304-3940(87)90353-3 ◽

1987 ◽

Vol 81 (1-2) ◽

pp. 133-138 ◽

Cited By ~ 4

Author(s):

Vitaly Vodyanoy ◽

Dominique Muller ◽

Kathryn Kramer ◽

Gary Lynch ◽

Michel Baudry

Keyword(s):

Lipid Bilayers ◽

Artificial Lipid Bilayers

Download Full-text

Comparison of large-conductance Ca(2+)-activated K+ channels in artificial bilayer and patch-clamp experiments

AJP Cell Physiology ◽

10.1152/ajpcell.1994.266.3.c601 ◽

1994 ◽

Vol 266 (3) ◽

pp. C601-C610 ◽

Cited By ~ 6

Author(s):

C. L. Kapicka ◽

A. Carl ◽

M. L. Hall ◽

A. L. Percival ◽

B. W. Frey ◽

...

Keyword(s):

Lipid Bilayers ◽

Apparent Distance ◽

Bk Channels ◽

Open Probability ◽

K Channels ◽

Artificial Lipid Bilayers ◽

Excised Patches ◽

Lipid Environment ◽

Artificial Bilayers ◽

Channel Properties

We compared the gating, ion conduction, and pharmacology of large-conductance Ca(2+)-activated K+ channels (BK channels) from canine colon in artificial lipid bilayers and in excised patches. Both protocols identified 270-pS K(+)-selective channels activated by depolarization and Ca2+ (approximately 130-mV shift of half-activation voltage per 10-fold change in Ca2+) that were inhibited by extracellular tetraethylammonium (TEA) and charybdotoxin. These similarities suggest that the same BK channels are studied in the two techniques. However, we found three quantitative differences between channels in artificial bilayers and patches. 1) Channels in artificial bilayers required fivefold higher free Ca2+ or 80-mV stronger depolarization for activation. 2) The voltage dependence of TEA block was smaller for channels in artificial bilayers. The apparent distance across the membrane field for the TEA binding site was 0.031 for channels in artificial bilayers and 0.23 for channels in patches. 3) ATP (2 mM) decreased open probability (Po) of channels in artificial bilayers, whereas channels in patches were unaffected. Neither GTP nor UTP reduced Po of channels in artificial bilayers. It is possible that these differences may be due to a lack of molecular identity between the channels studied in the two protocols. Alternatively, they may be attributed to alterations in channel properties during reconstitution or to influences of the artificial lipid environment.

Download Full-text