title: Mannose 6 dephosphorylation of lysosomal proteins mediated by acid phosphatases Acp2 and Acp5.
abstract: Mannose 6-phosphate (Man6P) residues represent a recognition signal required for efficient receptor-dependent transport of soluble lysosomal proteins to lysosomes. Upon arrival, the proteins are rapidly dephosphorylated. We used mice deficient for the lysosomal acid phosphatase Acp2 or Acp5 or lacking both phosphatases (Acp2/Acp5(-/-)) to examine their role in dephosphorylation of Man6P-containing proteins. Two-dimensional (2D) Man6P immunoblot analyses of tyloxapol-purified lysosomal fractions revealed an important role of Acp5 acting in concert with Acp2 for complete dephosphorylation of lysosomal proteins. The most abundant lysosomal substrates of Acp2 and Acp5 were identified by Man6P affinity chromatography and mass spectrometry. Depending on the presence of Acp2 or Acp5, the isoelectric point of the lysosomal cholesterol-binding protein Npc2 ranged between 7.0 and 5.4 and may thus regulate its interaction with negatively charged lysosomal membranes at acidic pH. Correspondingly, unesterified cholesterol was found to accumulate in lysosomes of cultured hepatocytes of Acp2/Acp5(-/-) mice. The data demonstrate that dephosphorylation of Man6P-containing lysosomal proteins requires the concerted action of Acp2 and Acp5 and is needed for hydrolysis and removal of degradation products.
authors.affiliation: Department of Biochemistry, Children’s Hospital, University Medical Center Hamburg-Eppendorf, Hamburg, Germany.
authors.forename: Georgia
authors.initials: G
authors.lastname: Makrypidi
authors.forename: Markus
authors.initials: M
authors.lastname: Damme
authors.forename: Sven
authors.initials: S
authors.lastname: Müller-Loennies
authors.forename: Maria
authors.initials: M
authors.lastname: Trusch
authors.forename: Bernhard
authors.initials: B
authors.lastname: Schmidt
authors.forename: Hartmut
authors.initials: H
authors.lastname: Schlüter
authors.forename: Joerg
authors.initials: J
authors.lastname: Heeren
authors.forename: Torben
authors.initials: T
authors.lastname: Lübke
authors.forename: Paul
authors.initials: P
authors.lastname: Saftig
authors.forename: Thomas
authors.initials: T
authors.lastname: Braulke
mesh_terms: D000135:Acid Phosphatase / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D002784:Cholesterol / Q000378:metabolism; D015180:Electrophoresis, Gel, Two-Dimensional; D022781:Hepatocytes / Q000378:metabolism; D007527:Isoenzymes / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D008360:Mannosephosphates / Q000378:metabolism*; D051379:Mice; D018345:Mice, Knockout; D010766:Phosphorylation; D011506:Proteins / Q000737:chemistry / Q000378:metabolism*; D053719:Tandem Mass Spectrometry; D000071681:Tartrate-Resistant Acid Phosphatase; D033921:Vesicular Transport Proteins / Q000737:chemistry / Q000378:metabolism
chemical_list: D007527:Isoenzymes; D008360:Mannosephosphates; C497045:Npc2 protein, mouse; D011506:Proteins; D033921:Vesicular Transport Proteins; C018589:lysosomal proteins; C027693:mannose-6-phosphate; D002784:Cholesterol; D000135:Acid Phosphatase; C520785:Acp2 protein, mouse; C000605511:Acp5 protein, mouse; D000071681:Tartrate-Resistant Acid Phosphatase