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J. Biol. Chem., Vol. 281, Issue 7, 3785-3792, February 17, 2006
Golgi Localization Determinants in ArfGAP1 and in New Tissue-specific ArfGAP1 Isoforms*From the Department of Biology, Technion-Israel Institute of Technology, Haifa 32000, Israel The Arf1-directed GTPase-activating protein ArfGAP1 is a Golgi-localized protein that controls the dynamics of the COPI coat of carriers that mediate transport in the endoplasmic reticulum-Golgi shuttle. Previously the interaction of ArfGAP1 with the Golgi was allocated to a portion of the non-catalytic, carboxyl part of the protein, but the mechanism of this interaction has not been established. In this study we identify a short stretch in the non-catalytic part of ArfGAP1 (residues 204214) in which several hydrophobic residues contribute to Golgi localization. Even single alanine replacement of two of these residues (Leu-207 and Trp-211) strongly diminished Golgi localization. Mutations in the hydrophobic residues also diminished the in vitro activity of ArfGAP1 on Arf1 bound to Golgi membranes. The stretch containing the hydrophobic residues was recently shown to mediate the binding of ArfGAP1 to loosely packed lipids of highly curved liposomes (Bigay, J., Casella, J. F., Drin, G., Mesmin, B., and Antonny, B. (2005) EMBO J. 24, 22442253). Whereas short fragments containing the hydrophobic stretch were not Golgi-localized, a proximal 10-residue in-frame insertion that is present in new ArfGAP1 isoforms that we identified in brain and heart tissues could confer Golgi localization on these fragments. This localization was abrogated by alanine replacement of residues Phe-240 or Trp-241 of the insertion sequence but not by their replacement with leucines. Our findings indicate that ArfGAP1 interacts with the Golgi through multiple hydrophobic motifs and that alternative modes of interaction may exist in tissue-specific ArfGAP1 isoforms.
Received for publication, August 15, 2005 , and in revised form, November 22, 2005. * This work was supported by a grant from the Israel Science Foundation (#448/04). The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. Section 1734 solely to indicate this fact. The nucleotide sequence(s) reported in this paper has been submitted to the GenBankTM/EBI Data Bank with accession number(s) DQ167810 [GenBank] and DQ167811 [GenBank] 1 These authors equally contributed to this work. 2 To whom correspondence should be addressed. Tel.: 9724-829-3408; Fax: 9724-822-5153; E-mail: danc{at}tx.technion.ac.il.
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