Premium
Analysis of the role of the leucine zipper motif in regulating the ability of AFAP‐110 to alter actin filament integrity
Author(s) -
Qian Yong,
Gatesman Amanda S.,
Baisden Joseph M.,
Zot Henry G.,
Cherezova Lidia,
Qazi Ihtishaam,
Mazloum Nayef,
Lee Marietta Y.,
GuapponeKoay Anne,
Flynn Daniel C.
Publication year - 2003
Publication title -
journal of cellular biochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.028
H-Index - 165
eISSN - 1097-4644
pISSN - 0730-2312
DOI - 10.1002/jcb.10725
Subject(s) - leucine zipper , actin , protein filament , microbiology and biotechnology , mutant , cytoskeleton , sequence motif , biology , peptide sequence , chemistry , biochemistry , gene , cell
AFAP‐110 has an intrinsic ability to alter actin filament integrity as an actin filament crosslinking protein. This capability is regulated by a carboxy terminal leucine zipper (Lzip) motif. The Lzip motif facilitates self‐association stabilizing the AFAP‐110 multimers. Deletion of the Lzip motif (AFAP‐110 Δlzip ) reduces the stability of the AFAP‐110 multimer and concomitantly increases its ability to crosslink actin filaments, in vitro, and to activate cSrc and alter actin filament integrity, in vivo. We sought to determine how the Lzip motif regulates AFAP‐110 function. Substitution of the c‐Fos Lzip motif in place of the AFAP‐110 Lzip motif (AFAP‐110 fos ) was predicted to preserve the α‐helical structure while changing the sequence. To alter the structure of the α‐helix, a leucine to proline mutation was generated in the AFAP‐110 α‐helical Lzip motif (AFAP‐110 581P ), which largely preserved the sequence. The helix mutants, AFAP‐110 Δlzip , AFAP‐110 fos , and AFAP‐110 581P , demonstrated reduced multimer stability with an increased capacity to crosslink actin filaments, in vitro, relative to AFAP‐110. An analysis of opposing binding sites indicated that the carboxy terminus/Lzip motif can contact sequences within the amino terminal pleckstrin homology (PH1) domain indicating an auto‐inhibitory mechanism for regulating multimer stability and actin filament crosslinking. In vivo, only AFAP‐110 Δlzip and AFAP‐110 581P were to activate cSrc and to alter cellular actin filament integrity. These data indicate that the intrinsic ability of AFAP‐110 to crosslink actin filaments is dependent upon both the sequence and structure of the Lzip motif, while the ability of the Lzip motif to regulate AFAP‐110‐directed activation of cSrc and changes in actin filament integrity in vivo is dependent upon the structure or presence of the Lzip motif. We hypothesize that the intrinsic ability of AFAP‐110 to crosslink actin filaments or activate cSrc are distinct functions. © 2003 Wiley‐Liss, Inc.