Neuroprotective Role of a Proline-Rich Akt Substrate in Apoptotic Neuronal Cell Death after Stroke: Relationships with Nerve Growth Factor

Abstract

The Akt signaling pathway contributes to regulation of apoptosis after a variety of cell death stimuli. A novel proline-rich Akt substrate (PRAS) was recently detected and found to be involved in apoptosis. In our study, Akt activation was modulated by growth factors, and treatment with nerve growth factor (NGF) reduced apoptotic cell death after ischemic injury. However, the role of the PRAS pathway in apoptotic neuronal cell death after ischemia remains unknown. Phosphorylated PRAS (pPRAS) and the binding of pPRAS/phosphorylated Akt (pPRAS/pAkt) to 14-3-3 (pPRAS/14-3-3) were detected, and their expression transiently decreased in mouse brains after transient focal cerebral ischemia (tFCI). Liposome-mediated pPRAS cDNA transfection induced overexpression of pPRAS, promoted pPRAS/14-3-3, and inhibited apoptotic neuronal cell death after tFCI. The expression of pPRAS, pPRAS/pAkt, and pPRAS/14-3-3 increased in NGF-treated mice but decreased with inhibition of phosphatidylinositol-3 kinase and the NGF receptor after tFCI. These results suggest that PRAS phosphorylation and its interaction with pAkt and 14-3-3 might play an important role in neuroprotection mediated by NGF in apoptotic neuronal cell death after tFCI.

Activation of the Akt/GSK3β Signaling Pathway Mediates Survival of Vulnerable Hippocampal Neurons after Transient Global Cerebral Ischemia in Rats

“…Akt/GSK3b signaling and delayed neuronal cell death H Endo et al ischemia include Bad (Saito et al, 2003), prolinerich Akt substrate (Saito et al, 2004), Forkhead transcription factors (Kawano et al, 2002), and endothelial nitric oxide synthase (Hashiguchi et al, 2004). The current study shows that GSK3b is also one of the targets of Akt in the PI3-K signaling pathway after cerebral ischemia.…”

Inhibition of c-jun N terminal kinase (JNK) improves functional beta cell mass in human islets and leads to AKT and glycogen synthase kinase-3 (GSK-3) phosphorylation

“…Since the integrity of the insulin signalling cascade in beta cells is responsible for preservation of beta cell mass and for insulin secretion [43], and since JNK inhibition affects IRS-1/AKT in peripheral tissues [13][14][15], we tested the effect of L-JNKI in human islet insulin pathway with our main focus on AKT and its substrates. Among those substrates, GSK-3B and p70S6K participate in the regeneration of beta cell mass via increased mitogenesis [44,45], while PRAS40 is also activated by insulin in peripheral tissues and is implicated in protection of neurons against ischaemic injury [46,47]. We found that JNK inhibition in human islets treated with either L-JNKI or SP600125 specifically stimulated the phosphorylation of AKT and GSK-3B (Fig.…”

“…L-JNKI did not affect PRAS40 either at baseline or after cytokine exposure. This was surprising, since the AKT-mediated protection against apoptosis of neurons exposed to an ischaemic event has been shown to be mediated by PRAS40 [47]. Similarly, L-JNKI did not affect p70S6K, although cytokines activated p70S6K similarly to results reported in adipocytes exposed to IL-1β [49].…”

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

“…Both the PRAS40 plasmid and plasmid pcDNA3.1( + ) vector were grown overnight, and plasmid was extracted using a Qiagen kit (Valencia, CA, USA). Both the PRAS40 plasmid and pcDNA3.1( + ) were mixed with cationic liposome DOTAP (Biontex, Germany) at the ratio of 1:2 (microgram of cDNA to microliter of liposome) and allowed to complex for 15 mins before injection, according to our previous study (Saito et al, 2004). We used an intracisternal injection because it has been shown to be acceptable up to 300 mL solution (Pulford et al, 1999;Solomon et al, 1985).…”