title: The small heat shock protein Hsp22 of Drosophila melanogaster is a mitochondrial protein displaying oligomeric organization.
abstract: Drosophila melanogaster has four main small heat shock proteins (Hsps), D. melanogaster Hsp22 (DmHsp22), Hsp23 (DmHsp23), Hsp26 (DmHsp26), and Hsp27 (DmHsp27). These proteins, although they have high sequence homology, show distinct developmental expression patterns. The function(s) of each small heat shock protein is unknown. DmHsp22 is shown to localize in mitochondria both in D. melanogaster S2 cells and after heterologous expression in mammalian cells. Fractionation of mitochondria indicates that DmHsp22 resides in the mitochondrial matrix, where it is found in oligomeric complexes, as shown by sedimentation and gel filtration analysis and by cross-linking experiments. Deletion analysis using a DmHsp22-EGFP construct reveals that residues 1-17 and an unknown number of residues between 17-28 are necessary for import. Site-directed mutagenesis within a putative mitochondrial motif (WRMAEE) at positions 8-13 shows that the first four residues are necessary for mitochondrial localization. Immunoprecipitation results indicate that there is no interaction between DmHsp22 and the other small heat shock proteins. The mitochondrial localization of this small Hsp22 of Drosophila and its high level of expression in aging suggests a role for this small heat shock protein in protection against oxidative stress.
authors.affiliation: Laboratoire de Génétique Cellulaire et Développementale, Département de Médecine, Pavillon Marchand, Université Laval, Ste-Foy, Quebec G1K 7P4, Canada.
authors.forename: G
authors.initials: G
authors.lastname: Morrow
authors.forename: Y
authors.initials: Y
authors.lastname: Inaguma
authors.forename: K
authors.initials: K
authors.lastname: Kato
authors.forename: R M
authors.initials: RM
authors.lastname: Tanguay
mesh_terms: D000596:Amino Acids / Q000737:chemistry; D000818:Animals; D019556:COS Cells; D002460:Cell Line; D002467:Cell Nucleus / Q000378:metabolism; D002499:Centrifugation, Density Gradient; D002850:Chromatography, Gel; D006224:Cricetinae; D003432:Cross-Linking Reagents / Q000378:metabolism; D029721:Drosophila Proteins; D004331:Drosophila melanogaster / Q000737:chemistry*; D004591:Electrophoresis, Polyacrylamide Gel; D017353:Gene Deletion; D005976:Glutaral / Q000494:pharmacology; D006367:HeLa Cells; D006360:Heat-Shock Proteins / Q000737:chemistry* / Q000235:genetics / Q000502:physiology*; D006358:Hot Temperature; D006801:Humans; D015151:Immunoblotting; D008856:Microscopy, Fluorescence; D008928:Mitochondria / Q000737:chemistry*; D018832:Molecular Chaperones; D016297:Mutagenesis, Site-Directed; D018384:Oxidative Stress; D011233:Precipitin Tests; D017346:Protein Serine-Threonine Kinases; D013347:Subcellular Fractions / Q000378:metabolism; D013997:Time Factors; D014357:Trypsin / Q000494:pharmacology
chemical_list: D000596:Amino Acids; D003432:Cross-Linking Reagents; D029721:Drosophila Proteins; C413214:HSPB8 protein, human; D006360:Heat-Shock Proteins; C490752:Hsp22 protein, Drosophila; D018832:Molecular Chaperones; D017346:Protein Serine-Threonine Kinases; D014357:Trypsin; D005976:Glutaral