Proteolytic processing of amyloid-beta precursor protein by secretases does not require cell surface transport.
Cleavage of amyloid-beta precursor protein (APP) by alpha-,beta-, and gamma-secretases releases an extracellular fragment called APPS, small Abeta peptides, and a short APP intracellular domain that may provide a transcriptional signal analogous to the Notch intracellular domain. Notch cleavage is activated by extracellular ligands on the cell surface, but the cellular localization of APP cleavage remains unclear. We now show that in transfected cultured cells, the plasma membrane SNARE protein syntaxin 1A, when expressed as a full-length protein, disrupts the Golgi apparatus and blocks trans-Golgi traffic and exocytosis. In contrast, truncated syntaxin 1A1-243 selectively abolishes exocytosis but has no apparent effect on trans-Golgi traffic or Golgi structure, whereas further truncated syntaxins 1A1-236 and 1A1-230 have no effect on either exocytosis or Golgi traffic. Using these syntaxin 1A fragments, we demonstrated that blocking trans-Golgi traffic greatly impairs APP cleavage and AICD-dependent nuclear signaling, whereas blocking exocytosis alone does not affect either process, even though secretion of APPS and Abeta40 peptide is abolished. Our data suggest that, different from Notch, cleavage of APP is independent of cell surface regulation by extracellular ligands but may be controlled by intracellular signaling.
Center for Basic Neuroscience, Department of Molecular Genetics, and Howard Hughes Medical Institute, The University of Texas Southwestern Medical Center, Dallas, Texas 75390-9111, USA.
Mikhail
M
Khvotchev
Thomas C
TC
Südhof
D016564:Amyloid beta-Protein Precursor / Q000737:chemistry / Q000378:metabolism*; D000818:Animals; D000954:Antigens, Surface / Q000737:chemistry*; D019556:COS Cells; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism*; D003470:Culture Media / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004591:Electrophoresis, Polyacrylamide Gel; D005089:Exocytosis; D006056:Golgi Apparatus / Q000378:metabolism; D006801:Humans; D015151:Immunoblotting; D008024:Ligands; D008565:Membrane Proteins / Q000378:metabolism*; D009419:Nerve Tissue Proteins / Q000737:chemistry*; D010455:Peptides / Q000737:chemistry; D010957:Plasmids / Q000378:metabolism; D017434:Protein Structure, Tertiary; D051381:Rats; D051880:Receptors, Notch; D015398:Signal Transduction; D050827:Syntaxin 1; D015533:Transcriptional Activation; D014162:Transfection
D016564:Amyloid beta-Protein Precursor; D000954:Antigens, Surface; D003470:Culture Media; D008024:Ligands; D008565:Membrane Proteins; D009419:Nerve Tissue Proteins; D010455:Peptides; D051880:Receptors, Notch; C494212:STX1A protein, human; C494213:Stx1a protein, rat; D050827:Syntaxin 1