title: Soluble amyloid precursor protein: a novel proliferation factor of adult progenitor cells of ectodermal and mesodermal origin.
abstract: BACKGROUND
  Soluble amyloid precursor protein α (sAPPα) is a proteolyte of APP cleavage by α-secretase. The significance of the cleavage and the physiological role of sAPPα are unknown. A crystal structure of a region of the amino terminal of sAPPα reveals a domain that is similar to cysteine-rich growth factors. While a previous study implicates sAPPα in the regulation of neural progenitor cell proliferation in the subventricular zone of adult mice, the ubiquitous expression of APP suggests that its role as a growth factor might be broader.
  
  
  METHODS
  sAPPα and α-secretase activities were determined in neural progenitor cells (NPCs), mesenchymal stem cells (MSC) and human decidua parietalis placenta stem cells (hdPSC). Inhibition of α-secretase was achieved by treatment with the matrixmetalloproteinase inhibitor GM6001, and proliferation was determined using clonogenic and immunocytochemical analysis of cell-lineage markers. Recovery of proliferation was achieved by supplementing GM6001-treated cells with recombinant soluble APPα. Expression of APP and its cellular localization in the subventricular zone was determined by Western blot and immunohistochemical analyses of APP wild type and knockout tissue. Alterations in pERK and pAKT expression as a function of soluble APPα production and activity in NPCs were determined by Western blot analysis.
  
  
  RESULTS
  Here we show that sAPPα is a proliferation factor of adult NPCs, MSCs and hdpPSC. Inhibition of α-secretase activity reduces proliferation of these stem cell populations in a dose-dependent manner. Stem cell proliferation can be recovered by the addition of sAPPα in a dose-dependent manner, but not of media depleted of sAPPα. Importantly, sAPPα operates independently of the prominent proliferation factors epidermal growth factor (EGF) and basic fibroblast growth factor (bFGF), but in association with ERK signaling and MAP-kinase signaling pathways. Levels of sAPPα and putative α-secretase, ADAM10, are particularly high in the subventricular zone of adult mice, suggesting a role for sAPPα in regulation of NPCs in this microenvironment.
  
  
  CONCLUSIONS
  These results determine a physiological function for sAPPα and identify a new proliferation factor of progenitor cells of ectodermal and mesodermal origin. Further, our studies elucidate a potential pathway for sAPPα signaling through MAP kinase activation.
authors: Department of Anatomy and Cell Biology, The University of Illinois at Chicago, 808 S Wood St, Rm, 572 Chicago, IL 60612, USA.
authors: Michael P
authors: MP
authors: Demars
authors: Amelia
authors: A
authors: Bartholomew
authors: Zuzana
authors: Z
authors: Strakova
authors: Orly
authors: O
authors: Lazarov
mesh_terms: D000328:Adult; D053687:Adult Stem Cells / Q000166:cytology / Q000502:physiology; D053829:Amyloid Precursor Protein Secretases / Q000378:metabolism; D016564:Amyloid beta-Protein Precursor / Q000502:physiology*; D000818:Animals; D049109:Cell Proliferation / Q000187:drug effects; D003656:Decidua / Q000166:cytology; D004151:Dipeptides / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004475:Ectoderm / Q000166:cytology; D004789:Enzyme Activation; D005260:Female; D006801:Humans; D020935:MAP Kinase Signaling System / Q000187:drug effects; D059630:Mesenchymal Stem Cells / Q000166:cytology / Q000502:physiology; D008648:Mesoderm / Q000166:cytology; D051379:Mice; D009474:Neurons / Q000166:cytology; D010446:Peptide Fragments / Q000502:physiology*; D011247:Pregnancy; D011480:Protease Inhibitors / Q000494:pharmacology
chemical_list: C545487:APP protein, human; D016564:Amyloid beta-Protein Precursor; D004151:Dipeptides; C078131:N-(2(R)-2-(hydroxamidocarbonylmethyl)-4-methylpentanoyl)-L-tryptophan methylamide; D010446:Peptide Fragments; D011480:Protease Inhibitors; D053829:Amyloid Precursor Protein Secretases