Rabbit Anti-ATF4 monoclonal antibody, clone TE31-03

Phosphoinositide 3-kinase gamma (PI3K gamma) expressed in immune cells is linked to neuroinflammation in several neurological diseases. However, the expression and role of PI3K gamma in preclinical traumatic brain injury (TBI) have not been investigated. In WT mice, we found that TBI induced rapid and extensive expression of PI3K gamma in neurons within the perilesional cortex and the ipsilateral hippocampal subfields (CA1, CA3), which peaked between 1 and 3 days and declined significantly 7 days after TBI. Intriguingly, the induction of neuronal PI3K gamma in these subregions of the brain spatiotemporally coincided with both the TBI-induced activation of the neuronal ER stress pathway (p-eIF2 alpha, ATF4, and CHOP) and neuronal cell death (marked by TUNEL-positive neurons) 3 days after TBI. Further, we show that the absence of PI3K gamma in knockout mice profoundly reduced the TBI-induced activation of the ER stress pathway and neuronal cell death. White matter disruption is a better predictor of long-term clinical outcomes than focal lesion size. We show that PI3K gamma deficiency not only reduced brain tissue loss but also alleviated white matter injury (determined by axonal injury and demyelination) up to 28 days after TBI. Importantly, PI3K gamma-knockout mice exhibited greater functional recovery including forepaw use, sensorimotor balance and coordination, and spatial learning and memory up to 28 days after TBI. These results unveil a previously unappreciated role for neuronal PI3K gamma in the regulation of ER stress associated with neuronal cell death, white matter damage, and long-term functional impairment after TBI.

Spontaneously regressing infantile haemangiomas and aggressive angiosarcomas are vascular tumours with excessive angiogenesis. When analysing haemangiomas and angiosarcomas immunohistochemically with respect to their chaperone profiles we found that angiosarcomas have significantly elevated protein levels of binding immunoglobulin protein (BIP) and PERK with concomitant attenuated IRE1 alpha levels, whereas haemangioma tissue exhibits the same pattern as embryonal skin tissue. We show that BiP is essential for the maintenance of VEGFR2 protein, which is expressed in the endothelium of both tumour types. When studying the effects of BiP, the IRE1 alpha/Xbp1 -, and PERK/ATF4-signalling pathways on the migration and tube-forming potential of endothelial cells, we show that downregulation of BiP, as well as inhibition of the kinase activity of IRE1 alpha, inhibit in vitro angiogenesis. Downregulation of PERK (PKR-like kinase; PKR = protein kinase R) levels promotes Xbp1 splicing in endoplasmic reticulum (ER)-stressed cells, indicating that in angiosarcoma the elevated PERK levels might result in high levels of unspliced Xbp1, which have been reported to promote cell proliferation and increase tumour malignancy. The data presented in this study revealed that in addition to BiP or PERK, the kinase domains of IRE1 alpha and Xbp1 could be potential targets for the development of novel therapeutic approaches for treating angiosarcomas and to control tumour angiogenesis. (c) 2020 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of Pathological Society of Great Britain and Ireland.