The BTB-kelch protein LZTR-1 is a novel Golgi protein that is degraded upon induction of apoptosis

J Biol Chem. 2006 Feb 24;281(8):5065-71. doi: 10.1074/jbc.M509073200. Epub 2005 Dec 15.

Abstract

Members of the BTB-kelch superfamily play important roles during fundamental cellular processes, such as the regulation of cell morphology, migration, and gene expression. The BTB-kelch protein LZTR-1 is deleted in the majority of DiGeorge syndrome patients and is believed to act as a transcriptional regulator. However, functional and expression profiling studies of LZTR-1 have not been performed thus far. Therefore, we examined the subcellular localization and function of LZTR-1 to gain insights into its biological role. Analysis of the primary structure of the protein revealed six N-terminal kelch motifs and two BTB/POZ domains at the C terminus within LZTR-1. Confocal analysis of the subcellular distribution of LZTR-1 using the Golgi markers GM130, Golgin-97, and TGN46 identified a localization of LZTR-1 exclusively on the cytoplasmic surface of the Golgi network that is mediated by its second BTB/POZ domain. In contrast to most other BTB-kelch proteins, LZTR-1 did not co-localize with actin. Treatment with brefeldin A did not lead to redistribution of LZTR-1 to the endoplasmic reticulum but caused its relocalization in dispersed, punctuated structures that were also positive for GM130. These data demonstrate that LZTR-1 is a Golgi matrix-associated protein. Upon induction of apoptosis, LZTR-1 was phosphorylated on tyrosine residues and subsequently degraded; that could be rescued partially by the addition of the caspase inhibitor Z-VAD-fmk and the proteasome inhibitors lactacystin and MG132. Taken together, our experiments identify LZTR-1 as the first BTB-kelch protein that exclusively localizes to the Golgi network, and the binding of LZTR-1 to the Golgi complex is mediated by its second BTB/POZ domain.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Actins / chemistry
  • Amino Acid Chloromethyl Ketones / pharmacology
  • Amino Acid Motifs
  • Amino Acid Sequence
  • Aorta / metabolism
  • Apoptosis*
  • Autoantigens / pharmacology
  • Blotting, Northern
  • Blotting, Western
  • Brefeldin A / pharmacology
  • Cell Line
  • Cells, Cultured
  • Cloning, Molecular
  • Endoplasmic Reticulum / metabolism
  • Endothelium, Vascular / metabolism
  • Golgi Apparatus / metabolism*
  • Golgi Matrix Proteins
  • HeLa Cells
  • Humans
  • Leupeptins / pharmacology
  • Membrane Glycoproteins / pharmacology
  • Membrane Proteins / pharmacology
  • Microscopy, Confocal
  • Molecular Sequence Data
  • Proteasome Endopeptidase Complex / metabolism
  • Protein Structure, Tertiary
  • Reverse Transcriptase Polymerase Chain Reaction
  • Transcription Factors / chemistry*
  • Transcription Factors / physiology*
  • Transcription, Genetic
  • Transfection
  • Tyrosine / chemistry
  • Ubiquitin / chemistry
  • Umbilical Veins / cytology

Substances

  • Actins
  • Amino Acid Chloromethyl Ketones
  • Autoantigens
  • Golgi Matrix Proteins
  • Golgi complex autoantigen, 97-kDa
  • Golgin subfamily A member 2
  • LZTR1 protein, human
  • Leupeptins
  • Membrane Glycoproteins
  • Membrane Proteins
  • TGOLN2 protein, human
  • Transcription Factors
  • Ubiquitin
  • benzyloxycarbonylvalyl-alanyl-aspartyl fluoromethyl ketone
  • Brefeldin A
  • Tyrosine
  • Proteasome Endopeptidase Complex
  • benzyloxycarbonylleucyl-leucyl-leucine aldehyde