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Keywords:

  • Alzheimer's disease;
  • α-Secretase;
  • APPα;
  • Proteasome;
  • Lactacystin;
  • Z-IE(Ot-Bu)A-leucinal;
  • Protein kinase C;
  • HK293 cells;
  • PC12 cells

Abstract

  1. Top of page
  2. Abstract

Abstract: The physiological processing of the β-amyloid precursor protein (βAPP) by a protease called α-secretase gives rise to APPα, a C-terminally truncated fragment of βAPP with known neurotrophic and cytoprotective properties. Several lines of evidence indicate that protein kinase C (PKC)-mediated events regulate this physiological pathway. We show here that the proteasome multicatalytic complex modulates the phorbol 12,13-dibutyrate-stimulated APPα secretion at several levels in human kidney 293 (HK293) cells. Two blocking agents of the proteasome, namely, Z-IE(Ot-Bu)A-leucinal and lactacystin, elicit a dual effect on PKC-regulated APPα secretion by metabolically labeled HK293 cells. Thus, short periods of preincubation (2–5 h) of the cells with the inhibitors trigger a drastic potentiation of APPα recovery, whereas long-term treatment of the cells (15–20 h) with the blocking agents leads to an overall decrease in the secretion of APPα. Such a dual effect was not observed on constitutive APPα secretion and intracellular formation generated by HK293 cells, which both only increase upon inhibitor treatments. Similar effects on the constitutive and PKC-regulated APPα secretion were observed with PC12 cells. Altogether, these data suggest distinct mechanisms underlying basal and PKC-regulated APPα production, indicating that this multicatalytic complex appears as a key contributor of the α-secretase pathway.

Abbreviations used: Aβ, β-amyloid peptide; APPα, C-terminally truncated fragment of β-amyloid precursor protein; βAPP, β-amyloid precursor protein; HK293, human kidney 293; mAb, monoclonal antibody; PDBu, phorbol 12,13-dibutyrate; PKC, protein kinase C; SDS-PAGE, sodium dodecyl sulfate-polyacrylamide gel electrophoresis; TBS, Tris-buffered saline; Z-IE(Ot-Bu)A-leucinal, N-benzyloxycarbonyl-Ile-Glu(O-tert-butyl)-Ala-leucinal.