title: TMP21 transmembrane domain regulates gamma-secretase cleavage.
abstract: TMP21 has been shown to be associated with the gamma-secretase complex and can specifically regulate gamma-cleavage without affecting epsilon-mediated proteolysis. To explore the basis of this activity, TMP21 modulation of gamma-secretase activity was investigated independent of epsilon-cleavage using an amyloid-beta precursor proteinepsilon (APPepsilon) construct which lacks the amyloid intracellular domain domain. The APPepsilon construct behaves similarly to the full-length precursor protein with respect to alpha- and beta-cleavages and is able to undergo normal gamma-processing. Co-expression of APPepsilon and TMP21 resulted in the accumulation of membrane-embedded higher molecular weight Abeta-positive fragments, consistent with an inhibition of gamma-secretase cleavage. The APPepsilon system was used to examine the functional domains of TMP21 through the investigation of a series of TMP21-p24a chimera proteins. It was found that chimeras containing the transmembrane domain bound to the gamma-secretase complex and could decrease gamma-secretase proteolytic processing. This was confirmed though investigation of a synthetic peptide corresponding to the TMP21 transmembrane helix. The isolated TMP21 TM peptide but not the homologous p24a domain was able to reduce Abeta production in a dose-dependent fashion. These observations suggest that the TMP21 transmembrane domain promotes its association with the presenilin complex that results in decreased gamma-cleavage activity.
authors.affiliation: Centre for Research in Neurodegenerative Diseases, University of Toronto, Toronto, Ontario M5S 3H2, Canada.
authors.forename: Raphaëlle
authors.initials: R
authors.lastname: Pardossi-Piquard
authors.forename: Christopher
authors.initials: C
authors.lastname: Böhm
authors.forename: Fusheng
authors.initials: F
authors.lastname: Chen
authors.forename: Soshi
authors.initials: S
authors.lastname: Kanemoto
authors.forename: Frédéric
authors.initials: F
authors.lastname: Checler
authors.forename: Gerold
authors.initials: G
authors.lastname: Schmitt-Ulms
authors.forename: Peter
authors.initials: P
authors.lastname: St George-Hyslop
authors.forename: Paul E
authors.initials: PE
authors.lastname: Fraser
mesh_terms: D053829:Amyloid Precursor Protein Secretases / Q000378:metabolism*; D016229:Amyloid beta-Peptides / Q000737:chemistry; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism; D002474:Cell-Free System; D004591:Electrophoresis, Polyacrylamide Gel; D004797:Enzyme-Linked Immunosorbent Assay; D017930:Genes, Reporter; D006801:Humans; D008239:Lysine / Q000737:chemistry; D008565:Membrane Proteins / Q000378:metabolism*; D016296:Mutagenesis; D029543:Nucleocytoplasmic Transport Proteins; D010455:Peptides / Q000737:chemistry*; D017434:Protein Structure, Tertiary; D011993:Recombinant Fusion Proteins / Q000737:chemistry
chemical_list: D016229:Amyloid beta-Peptides; D008565:Membrane Proteins; D029543:Nucleocytoplasmic Transport Proteins; D010455:Peptides; D011993:Recombinant Fusion Proteins; C484395:TMED10 protein, human; D053829:Amyloid Precursor Protein Secretases; D008239:Lysine