Therapeutic benefits of intrathecal protein therapy in a mouse model of amyotrophic lateral sclerosis

When fused with the protein transduction domain (PTD) derived from the human immunodeficiency virus TAT protein, proteins can cross the blood-brain barrier and cell membrane and transfer into several tissues, including the brain, making protein therapy feasible for various neurological disorders. We have constructed a powerful antiapoptotic modified Bcl-X_L protein (originally constructed from Bcl-X_L) fused with PTD derived from TAT (TAT-modified Bcl-X_L), and, to examine its clinical effectiveness in a mouse model of familial amyotrophic lateral sclerosis (ALS), transgenic mice expressing human Cu/Zn superoxide dismutase (SOD1) bearing a G93A mutation were treated by intrathecal infusion of TAT-modified Bcl-X_L. We demonstrate that intrathecally infused TAT-fused protein was effectively transferred into spinal cord neurons, including motor neurons, and that intrathecal infusion of TAT-modified Bcl-X_L delayed disease onset, prolonged survival, and improved motor performance. Histological studies show an attenuation of motor neuron loss and a decrease in the number of cleaved caspase 9-, cleaved caspase 3-, and terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL)-positive cells in the lumbar cords of TAT-modified Bcl-X_L-treated G93A mice. Our results indicate that intrathecal protein therapy using a TAT-fused protein is an effective clinical tool for the treatment of ALS.