Developmentally regulated mannose 6-phosphate receptor-mediated transport of a lysosomal enzyme across the blood-brain barrier.
Mucopolysaccharidosis type VII is a lysosomal storage disorder resulting from inherited deficiency of beta-glucuronidase (GUS). Mucopolysaccharidosis type VII is characterized by glycosaminoglycan storage in most tissues, including brain. In these disorders, enzyme delivery across the blood-brain barrier (BBB) is the main obstacle to correction of lysosomal storage in the CNS. Prior studies suggested mouse brain is accessible to GUS in the first 2 weeks of life but not later. To explore a possible role for the mannose 6-phosphate/insulin-like growth factor II receptor in GUS transport across the BBB in neonatal mice, we compared brain uptake of phosphorylated GUS (P-GUS) and nonphosphorylated GUS (NP-GUS) in newborn and adult mice. (131)I-P-GUS was transported across the BBB after i.v. injection in 2-day-old mice. The brain influx rate (K(in)) of (131)I-P-GUS in 2-day-old mice was 0.21 microl/g.min and decreased with age. By 7 weeks of age, transport of (131)I-P-GUS was not significant. Capillary depletion revealed that 62% of the (131)I-P-GUS in brain was in brain parenchyma in 2-day-old mice. In addition, uptake of (131)I-P-GUS into brain was significantly reduced by coinjection of unlabeled P-GUS or M6P in a dose-dependent manner. In contrast, the K(in) of (131)I-NP-GUS (0.04 microl/g.min) was significantly lower than (131)I-P-GUS in 2-day-old mice. Transcardiac brain perfusion confirmed that neither (131)I-P-GUS nor (131)I-NP-GUS crossed the BBB in adult mice. These results indicate that (131)I-P-GUS transport into brain parenchyma in early postnatal life is mediated by the mannose 6-phosphate/insulin-like growth factor II receptor. This receptor-mediated transport is not observed in adult mice.
Urayama
Akihiko
A
Department of Internal Medicine, Division of Geriatric Medicine, Saint Louis University School of Medicine, St. Louis, MO 63106, USA.
Grubb
Jeffrey H
JH
Sly
William S
WS
Banks
William A
WA
D000818:Animals; D000831:Animals, Newborn; D001812:Blood-Brain Barrier / Q000502:physiology*; D001921:Brain / Q000378:metabolism; D005966:Glucuronidase / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D007457:Iodine Radioisotopes / Q000378:metabolism; D008247:Lysosomes / Q000201:enzymology*; D008297:Male; D051379:Mice; D008815:Mice, Inbred Strains; D021381:Protein Transport / Q000502:physiology; D017527:Receptor, IGF Type 2 / Q000378:metabolism*; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D012709:Serum Albumin / Q000378:metabolism; D013997:Time Factors
D007457:Iodine Radioisotopes; D017527:Receptor, IGF Type 2; D011994:Recombinant Proteins; D012709:Serum Albumin; D005966:Glucuronidase