title: Transmembrane prostatic acid phosphatase (TMPAP) delays cells in G1 phase of the cell cycle.
abstract: BACKGROUND
  Prostate adenocarcinoma is the most common form of prostate cancer. We have previously shown in a murine model that prostatic acid phosphatase (PAP) deficiency leads to increased cell proliferation and development of prostate adenocarcinoma. The association between PAP and prostate cancer has been reported. Indeed, high PAP enzymatic activity is detected in the serum of patients with metastatic disease while its expression is reduced in prostate cancer tissue. However, the molecular mechanisms behind the onset of the disease remains poorly understood. We previously identified a novel transmembrane prostatic acid phosphatase (TMPAP) isoform, which interacts with snapin. TMPAP is expressed on the plasma membrane, as well as endosomal/lysosomal and exosomal membrane vesicles by means of a tyrosine-based lysosomal targeting motif (Yxxϕ).
  
  
  METHODS
  We used stable overexpression of the secreted isoform (SPAP) and TMPAP in LNCaP cells, live cell imaging, microarray and qRT-PCR analyses, and fluid phase uptake of HRP and transferrin.
  
  
  RESULTS
  Our results indicate that the stable overexpression of TMPAP, but not SPAP in LNCaP cells reduces cell growth while increasing endo/exocytosis and cell size. Specifically, cells overexpressing TMPAP accumulate in the G1 phase of the cell cycle, and show altered gene expression profile.
  
  
  CONCLUSIONS
  Our data suggests that TMPAP may function as a non-canonical tumor suppressor by delaying cell growth in G1 phase of the cell cycle.
authors.affiliation: Department of Clinical Chemistry, University of Helsinki and Helsinki University Hospital Laboratory, FI-00014 University of Helsinki, Finland.
authors.forename: César L
authors.initials: CL
authors.lastname: Araujo
authors.affiliation: Department of Clinical Chemistry, University of Helsinki and Helsinki University Hospital Laboratory, FI-00014 University of Helsinki, Finland.
authors.forename: Ileana B
authors.initials: IB
authors.lastname: Quintero
authors.affiliation: Research Programs Unit, Genome-scale Biology and Institute of Biomedicine, FI-00014 University of Helsinki, Finland.
authors.forename: Kristian
authors.initials: K
authors.lastname: Ovaska
authors.affiliation: Department of Clinical Chemistry, University of Helsinki and Helsinki University Hospital Laboratory, FI-00014 University of Helsinki, Finland.
authors.forename: Annakaisa M
authors.initials: AM
authors.lastname: Herrala
authors.affiliation: Research Programs Unit, Genome-scale Biology and Institute of Biomedicine, FI-00014 University of Helsinki, Finland.
authors.forename: Sampsa
authors.initials: S
authors.lastname: Hautaniemi
authors.affiliation: Department of Clinical Chemistry, University of Helsinki and Helsinki University Hospital Laboratory, FI-00014 University of Helsinki, Finland.
authors.forename: Pirkko T
authors.initials: PT
authors.lastname: Vihko
mesh_terms: D000135:Acid Phosphatase / Q000096:biosynthesis*; D002453:Cell Cycle / Q000502:physiology; D045744:Cell Line, Tumor; D002462:Cell Membrane / Q000201:enzymology* / Q000473:pathology; D049109:Cell Proliferation / Q000502:physiology; D016193:G1 Phase / Q000502:physiology*; D006801:Humans; D008297:Male; D011471:Prostatic Neoplasms / Q000201:enzymology* / Q000473:pathology
chemical_list: D000135:Acid Phosphatase; C428439:prostatic acid phosphatase
keywords: cell growth; lysosomes; vesicular traffic