Characterization of detergent-insoluble complexes containing the familial Alzheimer's disease-associated presenilins.
Many cases of early-onset familial Alzheimer's disease have been linked to mutations within two genes encoding the proteins presenilin-1 and presenilin-2. The presenilins are 48-56-kDa proteins that can be proteolytically cleaved to generate an N-terminal fragment (approximately 25-35 kDa) and a C-terminal fragment (approximately 17-20 kDa). The N- and C-terminal fragments of presenilin-1, but not full-length presenilin-1, were readily detected in both human and mouse cerebral cortex and in neuronal and glioma cell lines. In contrast, presenilin-2 was detected almost exclusively in cerebral cortex as the full-length molecule with a molecular mass of 56 kDa. The association of the presenilins with detergent-insoluble, low-density membrane microdomains, following the isolation of these structures from cerebral cortex by solubilization in Triton X-100 and subsequent sucrose density gradient centrifugation, was also examined. A minor fraction (10%) of both the N- and C-terminal fragments of presenilin-1 was associated with the detergent-insoluble, low-density membrane microdomains, whereas a considerably larger proportion of full-length presenilin-2 was present in the same membrane microdomains. In addition, a significant proportion of full-length presenilin-2 was present in a high-density, detergent-insoluble cytoskeletal pellet enriched in beta-actin. The presence of the presenilins in detergent-insoluble, low-density membrane microdomains indicates a possible role for these specialized regions of the membrane in the lateral separation of Alzheimer's disease-associated proteins within the lipid bilayer and/or in the distinct functions of these proteins.
Parkin
E T
ET
School of Biochemistry and Molecular Biology, University of Leeds, England, UK.
Hussain
I
I
Karran
E H
EH
Turner
A J
AJ
Hooper
N M
NM
D000199:Actins / Q000032:analysis; D000544:Alzheimer Disease / Q000378:metabolism*; D000595:Amino Acid Sequence; D000818:Animals; D002451:Cell Compartmentation / Q000502:physiology; D002540:Cerebral Cortex / Q000737:chemistry* / Q000166:cytology / Q000378:metabolism; D003599:Cytoskeleton / Q000378:metabolism; D003902:Detergents; D005910:Glioma; D006801:Humans; D008565:Membrane Proteins / Q000032:analysis* / Q000235:genetics / Q000378:metabolism; D051379:Mice; D008969:Molecular Sequence Data; D009447:Neuroblastoma; D009474:Neurons / Q000737:chemistry / Q000378:metabolism; D010446:Peptide Fragments / Q000032:analysis; D053764:Presenilin-1; D053766:Presenilin-2; D012995:Solubility; D014407:Tumor Cells, Cultured / Q000737:chemistry / Q000378:metabolism
D000199:Actins; D003902:Detergents; D008565:Membrane Proteins; C508853:PSEN1 protein, human; C508861:PSEN2 protein, human; D010446:Peptide Fragments; D053764:Presenilin-1; D053766:Presenilin-2