IGF-1:tetanus toxin fragment C fusion protein improves delivery of IGF-1 to spinal cord but fails to prolong survival of ALS mice.
To improve delivery of human insulin-like growth factor-1 (hIGF-1) to brain and spinal cord, we generated a soluble IGF-1:tetanus toxin fragment C fusion protein (IGF-1:TTC) as a secreted product from insect cells. IGF-1:TTC exhibited IGF-1 and TTC activity in vitro; it increased levels of immunoreactive phosphoAkt in treated MCF-7 cells and bound to immobilized ganglioside GT1b. In mice, the fusion protein underwent retrograde transport by spinal cord motor neurons following intramuscular injection, and exhibited both TTC- and IGF-1 activity in the CNS following intrathecal infusion. Analogous to the case with TTC, intrathecal infusion of the fusion protein resulted in substantial levels of IGF-1:TTC in spinal cord tissue extracts. Tissue concentrations of hIGF-1 in lumbar spinal cords of mice infused with IGF-1:TTC were estimated to be approximately 500-fold higher than those in mice treated with unmodified recombinant hIGF-1 (rhIGF-1). Like rhIGF-1, infusion of IGF-1:TTC reduced levels of IGF-1 receptor immunoreactivity in the same extracts. Despite raising levels of exogenous hIGF-1 in spinal cord, intramuscular- or intrathecal administration of IGF-1:TTC had no significant effect on disease progression or survival of high-expressing SOD1(G93A) transgenic mice. IGF-1:TTC may prove to be neuroprotective in other animal models of CNS disease or injury known to be responsive to unmodified IGF-1.
Chian
Ru-Ju
RJ
Cecil B. Day Laboratory for Neuromuscular Research, Department of Neurology, Massachusetts General Hospital, Building 114, 16th Street, Room 3003, Charlestown, MA 02129, USA.
Li
Jianhong
J
Ay
Ilknur
I
Celia
Samuel A
SA
Kashi
Brenda B
BB
Tamrazian
Eric
E
Matthews
Jonathan C
JC
Bronson
Roderick T
RT
Rossomando
Anthony
A
Pepinsky
R Blake
RB
Fishman
Paul S
PS
Brown
Robert H
RH
Francis
Jonathan W
JW
D000690:Amyotrophic Lateral Sclerosis / Q000188:drug therapy / Q000401:mortality* / Q000473:pathology; D000818:Animals; D016367:Baculoviridae / Q000235:genetics; D002478:Cells, Cultured; D018450:Disease Progression; D016503:Drug Delivery Systems / Q000379:methods*; D005260:Female; D005822:Genetic Vectors / Q000008:administration & dosage / Q000235:genetics / Q000627:therapeutic use; D006801:Humans; D007273:Injections, Intramuscular; D007278:Injections, Spinal; D007334:Insulin-Like Growth Factor I / Q000008:administration & dosage* / Q000235:genetics / Q000627:therapeutic use; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D009046:Motor Neurons / Q000378:metabolism / Q000473:pathology*; D010446:Peptide Fragments / Q000008:administration & dosage* / Q000235:genetics / Q000627:therapeutic use; D011993:Recombinant Fusion Proteins / Q000008:administration & dosage* / Q000235:genetics / Q000627:therapeutic use; D013116:Spinal Cord / Q000378:metabolism / Q000473:pathology; D018411:Spodoptera / Q000235:genetics; D013744:Tetanus Toxin / Q000008:administration & dosage* / Q000235:genetics / Q000627:therapeutic use
D010446:Peptide Fragments; D011993:Recombinant Fusion Proteins; D013744:Tetanus Toxin; C040635:tetanus toxin fragment C; D007334:Insulin-Like Growth Factor I