title: ATP stimulates lysosomal sulphate transport at neutral pH: evidence for phosphorylation of the lysosomal sulphate carrier.
abstract: ATP markedly stimulated sulphate uptake by rat liver lysosomes that had been treated with N-ethylmaleimide to block the effects of the lysosomal proton-translocating ATPase (H+-ATPase). Maximal stimulation required millimolar concentrations of ATP and neutral buffer pH. ATP-stimulated transport exhibited saturation kinetics with a Km of 175 microM, identical with the Km for lysosomal sulphate uptake at pH 5.0, a process that does not require ATP. The requirement for ATP was specific: other nucleotides such as AMP, ADP, CTP, GTP, ITP and UTP failed to stimulate transport. Adenosine 5'-[beta,gamma-imido]triphosphate, the non-hydrolysable analogue of ATP, also failed to stimulate sulphate uptake, suggesting a requirement for ATP hydrolysis. Lysosomal pH, membrane potential and glucose transport were unchanged by the presence of ATP under the experimental conditions, consistent with a direct effect of ATP on the sulphate transporter. Exposure of lysosomes to protein kinase A and protein kinase C inhibitors did not alter the stimulation of sulphate transport by ATP. The lysosomal sulphate transport protein might be subject to regulation by a phosphorylation pathway that is not dependent on protein kinase A or protein kinase C.
authors.affiliation: Division of Medical Genetics, Department of Pediatrics, Harbor-UCLA Medical Center, 1124 West Carson Street, Torrance, CA 90502, USA.
authors.forename: H F
authors.initials: HF
authors.lastname: Chou
authors.forename: M
authors.initials: M
authors.lastname: Passage
authors.forename: A J
authors.initials: AJ
authors.lastname: Jonas
mesh_terms: D000227:Adenine Nucleotides / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000378:metabolism*; D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D002352:Carrier Proteins / Q000378:metabolism*; D017868:Cyclic AMP-Dependent Protein Kinases / Q000037:antagonists & inhibitors; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005947:Glucose / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D066298:In Vitro Techniques; D008099:Liver / Q000378:metabolism / Q000648:ultrastructure; D008247:Lysosomes / Q000187:drug effects / Q000378:metabolism*; D008564:Membrane Potentials; D026901:Membrane Transport Proteins; D010766:Phosphorylation; D011493:Protein Kinase C / Q000037:antagonists & inhibitors; D006180:Proton-Translocating ATPases / Q000378:metabolism; D051381:Rats; D000076988:Sulfate Transporters; D013431:Sulfates / Q000378:metabolism*
chemical_list: D000227:Adenine Nucleotides; D002352:Carrier Proteins; D004791:Enzyme Inhibitors; D026901:Membrane Transport Proteins; C085609:SLC26A4 protein, human; D000076988:Sulfate Transporters; D013431:Sulfates; D000255:Adenosine Triphosphate; D017868:Cyclic AMP-Dependent Protein Kinases; D011493:Protein Kinase C; D006180:Proton-Translocating ATPases; D005947:Glucose