Gelsolin binds to polyphosphoinositide-free lipid vesicles and simultaneously to actin microfilaments.
Gelsolin is a calcium-, pH- and lipid-dependent actin filament severing/capping protein whose main function is to regulate the assembly state of the actin cytoskeleton. Gelsolin is associated with membranes in cells, and it is generally assumed that this interaction is mediated by PPIs (polyphosphoinositides), since an interaction with these lipids has been characterized in vitro. We demonstrate that non-PPI lipids also bind gelsolin, especially at low pH. The data suggest further that gelsolin becomes partially buried in the lipid bilayer under mildly acidic conditions, in a manner that is not dependent of the presence of PPIs. Our data also suggest that lipid binding involves a number of sites that are spread throughout the gelsolin molecule. Linker regions between gelsolin domains have been implicated by other work, notably the linker between G1 and G2 (gelsolin domains 1 and 2 respectively), and we postulate that the linker region between the N-terminal and C-terminal halves of gelsolin (between G3 and G4) is also involved in the interaction with lipids. This region is compatible with other studies in which additional binding sites have been located within G4-6. The lipid-gelsolin interactions reported in the present paper are not calcium-dependent, and are likely to involve significant conformational changes to the gelsolin molecule, as the chymotryptic digest pattern is altered by the presence of lipids under our conditions. We also report that vesicle-bound gelsolin is capable of binding to actin filaments, presumably through barbed end capping. Gelsolin bound to vesicles can nucleate actin assembly, but is less active in severing microfilaments.
Méré
Jocelyn
J
UMR 5539, CNRS Laboratoire de motilité cellulaire, Ecole Pratique des Hautes Etudes, Université de Montpellier 2, Place E. Bataillon, CC107, 34095 Montpellier Cedex 5, France.
Chahinian
Anne
A
Maciver
Sutherland K
SK
Fattoum
Abdellatif
A
Bettache
Nadir
N
Benyamin
Yves
Y
Roustan
Claude
C
D008841:Actin Cytoskeleton / Q000378:metabolism*; D000199:Actins / Q000378:metabolism*; D002918:Chymotrypsin / Q000378:metabolism; D018260:Gelsolin / Q000737:chemistry / Q000378:metabolism*; D006801:Humans; D006863:Hydrogen-Ion Concentration; D008051:Lipid Bilayers / Q000378:metabolism; D008081:Liposomes / Q000378:metabolism*; D008563:Membrane Lipids / Q000378:metabolism*; D018613:Microscopy, Confocal; D008856:Microscopy, Fluorescence; D010446:Peptide Fragments / Q000737:chemistry / Q000378:metabolism; D010743:Phospholipids / Q000378:metabolism*; D011485:Protein Binding; D011487:Protein Conformation; D025941:Protein Interaction Mapping; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000378:metabolism; D013329:Structure-Activity Relationship
D000199:Actins; D018260:Gelsolin; D008051:Lipid Bilayers; D008081:Liposomes; D008563:Membrane Lipids; D010446:Peptide Fragments; D010743:Phospholipids; D011993:Recombinant Fusion Proteins; D002918:Chymotrypsin