RRC ID 42353
Author Yamaguchi K, Hata K, Koseki K, Shiozaki K, Akita H, Wada T, Moriya S, Miyagi T.
Title Evidence for mitochondrial localization of a novel human sialidase (NEU4).
Journal Biochem J
Abstract Based on the human cDNA sequence predicted to represent the NEU4 sialidase gene in public databases, a cDNA covering the entire coding sequence was isolated from human brain and expressed in mammalian cells. The cDNA encodes two isoforms: one possessing an N-terminal 12-amino-acid sequence that is predicted to be a mitochondrial targeting sequence, and the other lacking these amino acids. Expression of the isoforms is tissue specific, as assessed by reverse transcription-PCR. Brain, muscle and kidney contained both isoforms; liver showed the highest expression, and the short form was predominant in this organ. In transiently transfected COS-1 cells, enzyme activity was markedly increased with gangliosides as well as with glycoproteins and oligosaccharides as substrates compared with the control levels. This differs from findings with other human sialidases. Although the isoforms were not distinguishable with regard to substrate specificity, they exhibited differential subcellular localizations. Immunofluorescence microscopy and biochemical fractionation demonstrated that an exogenously expressed haemagglutinin-tagged long form of NEU4 was concentrated in mitochondria in several human culture cell types, whereas the short form was present in intracellular membranes, indicating that the sequence comprising the N-terminal 12 amino acid residues acts as a targeting signal for mitochondria. Co-localization of the long form to mitochondria was further supported by efficient targeting of the N-terminal region fused to enhanced green fluorescent protein, and by the targeting failure of a mutant with an amino acid substitution in this region. NEU4 is possibly involved in regulation of apoptosis by modulation of ganglioside G(D3), which accumulates in mitochondria during apoptosis and is the best substrate for the sialidase.
Volume 390(Pt 1)
Pages 85-93
Published 2005-8-15
DOI 10.1042/BJ20050017
PII BJ20050017
PMID 15847605
PMC PMC1184564
MeSH Amino Acid Sequence Cell Line DNA, Complementary Gene Expression / physiology Humans Mitochondria / chemistry* Mitochondria / physiology Molecular Sequence Data Neuraminidase / chemistry* Neuraminidase / metabolism Protein Isoforms Substrate Specificity Tissue Distribution
IF 4.097
Times Cited 102
Human and Animal Cells COS-1(RCB0143)