Display Settings:

Format

Send to:

Choose Destination
Proc Natl Acad Sci U S A. 2007 Oct 9;104(41):16080-5. Epub 2007 Sep 27.

Disease-associated mutant alpha-actinin-4 reveals a mechanism for regulating its F-actin-binding affinity.

Author information

  • 1Renal and Translational Medicine Divisions, Department of Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, MA 02115, USA.

Abstract

Alpha-actinin-4 is a widely expressed protein that employs an actin-binding site with two calponin homology domains to crosslink actin filaments (F-actin) in a Ca(2+)-sensitive manner in vitro. An inherited, late-onset form of kidney failure is caused by point mutations in the alpha-actinin-4 actin-binding domain. Here we show that alpha-actinin-4/F-actin aggregates, observed in vivo in podocytes of humans and mice with disease, likely form as a direct result of the increased actin-binding affinity of the protein. We document that exposure of a buried actin-binding site 1 in mutant alpha-actinin-4 causes an increase in its actin-binding affinity, abolishes its Ca(2+) regulation in vitro, and diverts its normal localization from actin stress fibers and focal adhesions in vivo. Inactivation of this buried actin-binding site returns the affinity of the mutant to that of the WT protein and abolishes aggregate formation in cells. In vitro, actin filaments crosslinked by the mutant alpha-actinin-4 exhibit profound changes of structural and biomechanical properties compared with WT alpha-actinin-4. On a molecular level, our findings elucidate the physiological importance of a dynamic interaction of alpha-actinin with F-actin in podocytes in vivo. We propose that a conformational change with full exposure of actin-binding site 1 could function as a switch mechanism to regulate the actin-binding affinity of alpha-actinin and possibly other calponin homology domain proteins under physiological conditions.

PMID:
17901210
[PubMed - indexed for MEDLINE]
PMCID:
PMC2042165
Free PMC Article

Images from this publication.See all images (6)Free text

Fig. 1.
Fig. 2.
Fig. 3.
Fig. 4.
Fig. 5.
Fig. 6.
PubMed Commons home

PubMed Commons

0 comments
How to join PubMed Commons

    Supplemental Content

    Full text links

    Icon for HighWire Icon for PubMed Central
    Loading ...
    Write to the Help Desk