Your browser doesn't support javascript.
loading
Show: 20 | 50 | 100
Results 1 - 2 de 2
Filter
Add more filters










Database
Language
Publication year range
1.
Mol Ther ; 12(2): 345-52, 2005 Aug.
Article in English | MEDLINE | ID: mdl-16043103

ABSTRACT

We used recombinant forms of human beta-glucuronidase (GUS) purified from secretions from stably transfected CHO cells to compare the native enzyme to a GUS-Tat C-terminal fusion protein containing the 11-amino-acid HIV Tat protein transduction domain for: (1) susceptibility to endocytosis by cultured cells, (2) rate of clearance following intravenous infusion, and (3) tissue distribution and effectiveness in clearing lysosomal storage following infusion in the MPS VII mouse. We found: (1) Native GUS was more efficiently taken up by cultured human fibroblasts and its endocytosis was exclusively mediated by the M6P receptor. The GUS-Tat fusion protein showed only 30-50% as much M6P-receptor-mediated uptake, but also was taken up by adsorptive endocytosis through binding of the positively charged Tat peptide to cell surface proteoglycans. (2) GUS-Tat was less rapidly cleared from the circulation in the rat (t(1/2) = 13 min vs 7 min). (3) Delivery to most tissues of the MPS VII mouse was similar, but GUS-Tat was more efficiently delivered to kidney. Histology showed that GUS-Tat more efficiently reduced storage in renal tubules, retina, and bone. These studies demonstrate that Tat modification can extend the range of tissues corrected by infused enzyme.


Subject(s)
Gene Products, tat/metabolism , Glucuronidase/metabolism , Mucopolysaccharidosis VII/metabolism , Animals , CHO Cells , Cells, Cultured , Cricetinae , Cricetulus , Endocytosis , Fibroblasts/metabolism , Genetic Therapy , Glucuronidase/chemistry , Glucuronidase/genetics , Male , Mannosephosphates/metabolism , Mice , Mice, Transgenic , Mucopolysaccharidosis VII/genetics , Mucopolysaccharidosis VII/therapy , Rats , Rats, Sprague-Dawley , Recombinant Proteins/metabolism
2.
Diabetes ; 53(12): 3159-67, 2004 Dec.
Article in English | MEDLINE | ID: mdl-15561946

ABSTRACT

ATP-sensitive K+ channels (K(ATP) channels) control electrical activity in beta-cells and therefore are key players in excitation-secretion coupling. Partial suppression of beta-cell K(ATP) channels in transgenic (AAA) mice causes hypersecretion of insulin and enhanced glucose tolerance, whereas complete suppression of these channels in Kir6.2 knockout (KO) mice leads to hyperexcitability, but mild glucose intolerance. To test the interplay of hyperexcitability and dietary stress, we subjected AAA and KO mice to a high-fat diet. After 3 months on the diet, both AAA and KO mice converted to an undersecreting and markedly glucose-intolerant phenotype. Although Kir6.2 is expressed in multiple tissues, its primary functional consequence in both AAA and KO mice is enhanced beta-cell electrical activity. The results of our study provide evidence that, when combined with dietary stress, this hyperexcitability is a causal diabetic factor. We propose an "inverse U" model for the response to enhanced beta-cell excitability: the expected initial hypersecretion can progress to undersecretion and glucose-intolerance, either spontaneously or in response to dietary stress.


Subject(s)
Glucose Intolerance/physiopathology , Islets of Langerhans/physiopathology , Potassium Channels, Inwardly Rectifying/physiology , Animals , Blood Glucose/metabolism , Glucose Intolerance/drug therapy , Insulin/blood , Insulin/metabolism , Insulin Secretion , Islets of Langerhans/metabolism , Mice , Mice, Knockout , Potassium Channels, Inwardly Rectifying/deficiency , Potassium Channels, Inwardly Rectifying/genetics
SELECTION OF CITATIONS
SEARCH DETAIL
...