CALEB/NGC Interacts with the Golgi-associated Protein PIST

Burkhard Hassel,Matthias Schreff,Eva-Maria Stübe,Uta Blaich,Stefan Schumacher

doi:10.1074/jbc.m305577200

Abstract

CALEB/NGC is a neural member of the epidermal growth factor protein family expressed in axon and synapse-rich areas of the nervous system and shown to be important for neurite formation. It can bind to the extracellular matrix proteins tenascin-R and tenascin-C. Here we show that CALEB/NGC interacts with the Golgi-associated protein PIST. PIST was originally described as an interaction partner of the small GTPase TC10 and was then found to be Golgi-associated by binding to syntaxin-6 and to be important for the transport of frizzled proteins and the cystic fibrosis transmembrane conductance regulator to the plasma membrane. In addition, PIST was demonstrated to be involved in autophagy and linked to processes of neurodegeneration. CALEB/NGC interacts with PIST in the yeast two-hybrid system. This interaction can be confirmed by co-immunoprecipitations and co-localization studies. The juxtamembrane cytoplasmic peptide segment of CALEB/NGC, highly conserved during evolution, mediates the binding to PIST. CALEB/NGC co-localizes with PIST in the Golgi apparatus of transfected COS7 cells and in Golgi-derived vesicles after brefeldin A or nocodazole treatment. Co-localization studies in primary hippocampal cells and analysis of Purkinje cells of colchicine-treated rats, serving as an in vivo model system to block microtubule-dependent transport processes, support the view that PIST is an interaction partner of CALEB/NGC and implicate that this interaction may play a role in the intracellular transport of CALEB/NGC.

Highlights

CALEB/NGC is a neural transmembrane protein, which was originally discovered in a screen for novel molecules implicated in cell differentiation processes of the nervous system [1,2,3]
Two different PDZ domain proteins, TACIP18/syntenin-1 and p59/GRASP55, were discovered, which bind to the C terminus of pro-TGF-␣ and affect its targeting to the cell surface [11, 12]
GRASP55 was formerly shown to play a role in the stacking of the Golgi apparatus, and syntenin-1 had been published as an interaction partner for the C termini of several transmembrane proteins including syndecans, class B ephrins, EpH A7, neurexins, the anion exchanger AE2, neurofascin, different glutamate receptor subtypes, schwannomin, and the protein-tyrosine phosphatase ␩ [13,14,15,16,17,18,19,20,21]

Summary

Introduction

CALEB/NGC (chicken acidic leucine-rich EGF1-like domaincontaining brain protein/neuroglycan C) is a neural transmembrane protein, which was originally discovered in a screen for novel molecules implicated in cell differentiation processes of the nervous system [1,2,3]. In contrast to the transmembrane proteins frizzled 5, frizzled 8, CFTR, and ClC-3B, where the corresponding C termini bind to the PDZ domain of PIST, in the case of CALEB/NGC, the juxtamembrane cytoplasmic peptide segment mediates the interaction with this Golgi-associated protein.

Results

Conclusion