ZFIN ID: ZDB-PUB-050711-6
Differential localization and identification of a critical aspartate suggest non-redundant proteolytic functions of the presenlin in homologues SPPL2b and SPPL3
Krawitz, P., Haffner, C., Fluhrer, R., Steiner, H., Schmid, B., and Haass, C.
Date: 2005
Source: The Journal of biological chemistry   280(47): 39515-39523 (Journal)
Registered Authors: Haass, Christian, Schmid, Bettina
Keywords: presenilin, intramembrane proteolysis, signal peptide peptidase, {gamma}-secretase complex, Alzheimer’s disease, zebrafish
MeSH Terms:
  • Amino Acid Motifs
  • Amino Acid Sequence
  • Animals
  • Apoptosis
  • Aspartic Acid/chemistry
  • Aspartic Acid Endopeptidases/chemistry*
  • Aspartic Acid Endopeptidases/genetics
  • Aspartic Acid Endopeptidases/metabolism*
  • Catalytic Domain/genetics
  • Cell Line
  • DNA, Complementary/genetics
  • Endoplasmic Reticulum/metabolism
  • Endosomes/metabolism
  • Gene Targeting
  • Humans
  • Lysosomes/metabolism
  • Membrane Proteins/chemistry*
  • Membrane Proteins/genetics
  • Membrane Proteins/metabolism*
  • Molecular Sequence Data
  • Mutagenesis, Site-Directed
  • Phenotype
  • Presenilin-1
  • Protein Sorting Signals
  • RNA, Antisense/genetics
  • Recombinant Proteins/chemistry
  • Recombinant Proteins/genetics
  • Recombinant Proteins/metabolism
  • Sequence Homology, Amino Acid
  • Transfection
  • Zebrafish
  • Zebrafish Proteins/chemistry
  • Zebrafish Proteins/genetics
  • Zebrafish Proteins/metabolism
PubMed: 15998642 Full text @ J. Biol. Chem.
FIGURES
ABSTRACT
Signal peptide peptidase (SPP) is an unusual aspartyl protease, which mediates clearance of signal peptides by proteolysis within the endoplasmic reticulum (ER). Like presenilins, which provide the proteolytically active subunit of the g-secretase complex, SPP contains a critical GxGD motif in its C-terminal catalytic center. While SPP is known to be an aspartyl protease of the GxGD type, several presenilin homologues / SPP-like proteins (PSHs/SPPL) of unknown function have been identified by database searches. We now investigated the subcellular localization and a putative proteolytic activity of PSHs/SPPLs in cultured cells and in an in vivo model. We demonstrate that SPPL2b is targeted through the secretory pathway to endosomes/lysosomes while SPP and SPPL3 are restricted to the ER. As suggested by the differential subcellular localization of SPPL2b compared to SPP and SPPL3, we found distinct phenotypes upon antisense gripNA mediated knockdown in zebrafish. spp and sppl3 knockdowns in zebrafish result in cell death within the central nervous system, whereas reduction of sppl2b expression causes erythrocyte accumulation in an enlarged caudal vein. Moreover, expression of D/A mutations of the putative C-terminal active sites of spp, sppl2 and sppl3 produced phenocopies of the respective knockdown phenotypes. Thus our data suggest that all investigated PSHs/SPPLs are members of the novel family of GxGD aspartyl proteases. Furthermore, SPPL2b is shown to be the first member of the SPP/PSH/SPPL family, which is not located within the ER but in endosomal/ lysosomal vesicles.
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