Coordinated and widespread expression of gamma-secretase in vivo: evidence for size and molecular heterogeneity.
Gamma-secretase is a high molecular weight protein complex composed of four subunits, namely, presenilin (PS; 1 or 2), nicastrin, anterior pharynx defective-1 (Aph-1; A or B), and presenilin enhancer-2 (Pen-2), and is responsible for the cleavage of a number of type-1 transmembrane proteins. A fundamental question is whether different gamma-secretase complexes exist in vivo. We demonstrate here by in situ hybridization and by Northern and Western blotting that the gamma-secretase components are widely distributed in all tissues investigated. The expression of the different subunits seems tightly coregulated. However, some variation in the expression of the Aph-1 proteins is observed, Aph-1A being more general and abundantly distributed than Aph-1B. The previously uncharacterized rodent-specific Aph-1C mRNA is highly expressed in the kidney and testis but not in brain or other tissues, indicating some tissue specificity for the Aph-1 component of the gamma-secretase complex. Blue-native electrophoresis revealed size heterogeneity of the mature gamma-secretase complex in various tissues. Using co-immunoprecipitations and blue-native electrophoresis at endogenous protein levels, we find evidence that several independent gamma-secretase complexes can coexist in the same cell type. In conclusion, our results suggest that gamma-secretase is a heterogeneous family of protein complexes widely expressed in the adult organism.
Hébert
Sébastien S
SS
Neuronal Cell Biology and Gene Transfer, Center for Human Genetics, Flanders Interuniversity Institute for Biotechnology (VIB4) and K.U. Leuven, 3000 Leuven, Belgium.
Serneels
Lutgarde
L
Dejaegere
Tim
T
Horré
Katrien
K
Dabrowski
Michal
M
Baert
Veerle
V
Annaert
Wim
W
Hartmann
Dieter
D
De Strooper
Bart
B
D000595:Amino Acid Sequence; D053829:Amyloid Precursor Protein Secretases; D000818:Animals; D016282:Aspartic Acid Endopeptidases; D015153:Blotting, Western; D002460:Cell Line; D020090:Chromosome Segregation; D010450:Endopeptidases / Q000737:chemistry / Q000378:metabolism*; D006367:HeLa Cells; D006801:Humans; D007527:Isoenzymes / Q000378:metabolism; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism; D051379:Mice; D018345:Mice, Knockout; D008969:Molecular Sequence Data; D008970:Molecular Weight; D010447:Peptide Hydrolases; D053764:Presenilin-1; D053766:Presenilin-2; D020033:Protein Isoforms / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D014018:Tissue Distribution; D014162:Transfection
D007527:Isoenzymes; D008565:Membrane Proteins; C508853:PSEN1 protein, human; C508861:PSEN2 protein, human; C469349:PSENEN protein, human; D053764:Presenilin-1; D053766:Presenilin-2; D020033:Protein Isoforms; D012333:RNA, Messenger; C475154:APH1A protein, human; D053829:Amyloid Precursor Protein Secretases; D010450:Endopeptidases; D010447:Peptide Hydrolases; D016282:Aspartic Acid Endopeptidases; C509280:BACE1 protein, human; C509282:Bace1 protein, mouse