Targeting of SCG10 to the Area of the Golgi Complex Is Mediated by Its NH2-terminal Region

doi:10.1074/jbc.272.8.5175

Targeting of SCG10 to the Area of the Golgi Complex Is Mediated by Its NH₂-terminal Region*

From the ^‡ Geneva Biomedical Research Institute, Geneva, Switzerland,
^§ Glaxo Wellcome Inc., Research Triangle Park, North Carolina 27709, and the
^¶ Department of Biochemistry, Sciences II, 1211 Geneva 4, Switzerland

^∥ To whom correspondence should be addressed:
Geneva Biomedical Research Inst., 14, chemin des Aulx, Case Postale 674, 1228 Plan-les-Ouates/Geneva, Switzerland.
Tel.: 41-22-706-96-66; Fax: 41-22-794-69-65.

Abstract

SCG10 is a neuronal growth-associated protein that is concentrated in the growth cones of developing neurons. SCG10 shows a high degree of sequence homology to the ubiquitous phosphoprotein stathmin, which has been recently identified as a factor that destabilizes microtubules by increasing their catastrophe rate. Whereas stathmin is a soluble cytosolic protein, SCG10 is membrane-associated, indicating that the protein acts in a distinct subcellular compartment. Identifying the precise intracellular distribution of SCG10 as well as the mechanisms responsible for its specific targeting will contribute to elucidating its function. The main structural feature distinguishing the two proteins is that SCG10 contains an NH₂-terminal extension of 34 amino acids. In this study, we have examined the intracellular distribution of SCG10 in PC12 cells and in transfected COS-7 cells and the role of the NH₂-terminal domain in membrane-binding and intracellular targeting. SCG10 was found to be localized to the Golgi complex region. We show that the NH₂-terminal region (residues 1-34) was necessary for membrane targeting and Golgi localization. Fusion proteins consisting of the NH₂-terminal 34 amino acids of SCG10 and the related protein stathmin or the unrelated protein, β-galactosidase, accumulated in the Golgi, demonstrating that this sequence was sufficient for Golgi localization. Biosynthetic labeling of transfected COS-7 cells with [³H]palmitic acid revealed that two cysteine residues contained within the NH₂-terminal domain were sites of palmitoylation.

Footnotes

↵* The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
↵¹ The abbreviations used are:

NGF

nerve growth factor

mAb

monoclonal antibody

PAGE

polyacrylamide gel electrophoresis

PCR

polymerase chain reaction

WGA

wheat germ agglutinin

FITC

fluorescein isothiocyanate

PBS

phosphate-buffered saline

SCG-GAL

chimeric construct where the NH₂ terminus of SCG10 has been fused to the β-galactosidase moiety

SCG-STAT

chimeric construct where the NH₂ terminus of SCG10 has been fused to stathmin.
- Received June 7, 1996.
- Revision received December 5, 1996.