Compositions and methods for treating diabetes
The present invention provides an isolated population of cells containing an expressible nucleic acid encoding proinsulin containing a proinsulin cleavage site and a glucose-regulated expressible nucleic acid encoding a protease capable of cleaving the proinsulin cleavage site to produce insulin. The invention also provides an isolated population of cells which further express a hexosamine synthetic pathway enzyme. The invention additionally provides vectors containing an expressible nucleic acid encoding proinsulin containing a proinsulin cleavage site and a glucose-regulated expressible nucleic acid encoding a protease capable of cleaving the proinsulin cleavage site to produce insulin. The invention further provides a method of treating or preventing diabetes by implanting into an individual cells coexpressing proinsulin containing a proinsulin cleavage site and a glucose-regulated protease capable of cleaving the proinsulin cleavage site to produce insulin.
1. An isolated population of non-endocrine cells comprising an expressible nucleic acid encoding proinsulin containing a proinsulin cleavage site and a glucose-regulated expressible nucleic acid encoding an exogenous protease capable of cleaving said proinsulin cleavage site to produce insulin, wherein said cells express the hexosamine biosynthetic pathway enzyme glutamine:fructose-6-phosphate amidotransferase.
2. The isolated population of claim 1 , wherein said protease is furin.
3. The isolated population of claim 1 , wherein said glucose-regulated expressible nucleic acid further comprises a transforming growth factor-α(TGF-α) regulatory element.
4. The isolated population of claim 1 , wherein said proinsulin and said glucose-regulated protease are expressed from a single vector.
5. The isolated population of claim 4 , wherein said vector is a retroviral vector.
6. The isolated population of claim 4 , wherein said vector further comprises a selectable marker.
7. The isolated population of claim 1 , wherein said cells are smooth muscle cells.
8. The isolated population of claim 1 , wherein said proinsulin cleavage site further comprises the following tetrabasic sequence comprising the amino acids:
Arg-Xaa-Lys/Arg/Xaa-Arg (SEQ ID NO:7),
wherein Xaa comprises any amino acid.