Increased expression of a proline-rich Akt substrate (PRAS40) in human copper/zinc-superoxide dismutase transgenic rats protects motor neurons from death after spinal cord injury.
The serine-threonine kinase, Akt, plays an important role in the cell survival signaling pathway. A proline-rich Akt substrate, PRAS40, has been characterized, and an increase in phospho-PRAS40 (pPRAS40) is neuroprotective after transient focal cerebral ischemia. However, the involvement of PRAS40 in the cell death/survival pathway after spinal cord injury (SCI) is unclear. Liposome-mediated PRAS40 transfection was performed to study whether overexpression of pPRAS40 is neuroprotective. We further examined the expression of pPRAS40 after SCI by immunohistochemistry and Western blot using copper/zinc-superoxide dismutase (SOD1) transgenic (Tg) rats and wild-type (Wt) littermates. We then examined the relationship between PRAS40 and Akt by injection of LY294002, a phosphatidylinositol 3-kinase (PI3K) pathway inhibitor, or Akt inhibitor IV, a compound that inhibits Akt activation after SCI. Our data demonstrated that increased pPRAS40 resulted in survival of more motor neurons compared with control complementary DNA transfection. Phosphorylated PRAS40 increased in the Wt rats after SCI, whereas there was a greater and prolonged increase in the SOD1 Tg rats. Coimmunoprecipitation showed that binding of pPRAS40 with 14-3-3 increased 1 day after SCI in the Wt rats, whereas there was a significant increase in the Tg rats. The inhibitor studies showed that phospho-Akt and pPRAS40 were decreased after injection of LY294002 or Akt inhibitor IV. We conclude that an increase in pPRAS40 by transfection after SCI results in survival of motor neurons, and overexpression of SOD1 in the Tg rats results in an increase in endogenous pPRAS40 and a decrease in motor neuron death through the PI3K/Akt pathway.
Yu
Fengshan
F
Department of Neurosurgery, Stanford University School of Medicine, Stanford, California 94305-5487, USA.
Narasimhan
Purnima
P
Saito
Atsushi
A
Liu
Jing
J
Chan
Pak H
PH
D048868:Adaptor Proteins, Signal Transducing; D000818:Animals; D030801:Animals, Genetically Modified; D002545:Brain Ischemia / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D016923:Cell Death / Q000187:drug effects / Q000235:genetics; D002867:Chromones / Q000494:pharmacology; D004789:Enzyme Activation / Q000187:drug effects / Q000235:genetics; D004791:Enzyme Inhibitors / Q000494:pharmacology; D015870:Gene Expression; D006801:Humans; D009025:Morpholines / Q000494:pharmacology; D009046:Motor Neurons / Q000378:metabolism* / Q000473:pathology; D018696:Neuroprotective Agents / Q000378:metabolism*; D019869:Phosphatidylinositol 3-Kinases / Q000494:pharmacology; D000081082:Phosphoinositide-3 Kinase Inhibitors; D010750:Phosphoproteins / Q000096:biosynthesis* / Q000235:genetics; D010766:Phosphorylation / Q000187:drug effects; D051057:Proto-Oncogene Proteins c-akt / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D015398:Signal Transduction / Q000187:drug effects / Q000235:genetics; D013119:Spinal Cord Injuries / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D013482:Superoxide Dismutase / Q000096:biosynthesis* / Q000235:genetics; D000072105:Superoxide Dismutase-1; D013997:Time Factors; D014162:Transfection; D019076:Transgenes
D048868:Adaptor Proteins, Signal Transducing; D002867:Chromones; D004791:Enzyme Inhibitors; D009025:Morpholines; D018696:Neuroprotective Agents; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D010750:Phosphoproteins; D051057:Proto-Oncogene Proteins c-akt; D013482:Superoxide Dismutase; D000072105:Superoxide Dismutase-1; C516104:Akt1s1 protein, rat; C000606290:SOD1 protein, human; C085911:2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one; C000606292:Sod1 protein, rat