An Activated Protein C Analog Stimulates Neuronal Production by Human Neural Progenitor Cells via a PAR1-PAR3-S1PR₁-Akt Pathway

Abstract

Activated protein C (APC) is a protease with anticoagulant and cell-signaling activities. In the central nervous system, APC and its analogs with reduced anticoagulant activity but preserved cell signaling activities, such as 3K3A-APC, exert neuroprotective, vasculoprotective and anti-inflammatory effects. Murine APC promotes subependymal neurogenesis in rodents in vivo after ischemic and traumatic brain injury. Whether human APC can influence neuronal production from resident progenitor cells in humans is unknown. Here we show that 3K3A-APC, but not S360A-APC (an enzymatically inactive analog of APC), stimulated neuronal mitogenesis and differentiation from fetal human neural stem and progenitor cells (NPCs). 3K3A-APC’s effects on proliferation and differentiation were comparable to those respectively obtained with fibroblast growth factor and brain-derived growth factor. Its promoting effect on neuronal differentiation was accompanied by inhibition of astroglial differentiation. In addition, 3K3A-APC exerted modest anti-apoptotic effects during neuronal production. These effects appeared mediated through specific protease activated (PAR) and sphingosine-1-phosphate (S1PR) receptors, in that siRNA-mediated inhibition of PARs 1–4 and S1PRs 1–5 revealed that PAR1, PAR3 and S1PR1 are required for the neurogenic effects of 3K3A-APC. 3K3A-APC activated Akt, a downstream target of S1PR1, which was inhibited by S1PR1, PAR1 and PAR3 silencing. Adenoviral transduction of NPCs with a kinase-defective Akt mutant abolished the effects of 3K3A-APC on NPCs, confirming a key role of Akt activation in 3K3A-APC-mediated neurogenesis. Thus, APC and its pharmacological analogues, by influencing PAR and S1PR signals in resident neural progenitor cells, may be potent modulators of both development and repair in the human CNS.

PAR1 inhibition suppresses the self-renewal and growth of A2B5-defined glioma progenitor cells and their derived gliomas in vivo

“…That said, the attractiveness of PAR1 as a therapeutic target is tempered by its expression by normal astrocytic and neuronal populations alike, 52 as well as by resident neural stem cells. 53,54 Although tumor cells, and especially the tumor-initiating fraction thereof, selectively overexpress the receptor, its lower level basal expression by other normal cells of the central nervous system introduces the possibility of dose-dependent off-target effects that will mandate cautious titration in any therapeutic efforts targeting PAR1 itself. In that regard, those PAR1-targeted small molecules now available for clinical use, such as the novel direct PAR1 antagonist vorapaxar, have limited brain–barrier penetrance, further limiting current options for targeting PAR1-overexpressing TPCs.…”

Neurovascular dysfunction and neurodegeneration in dementia and Alzheimer's disease

“…APC also stimulates post-ischemic brain angiogenesis, vascular repair and neurogenesis [188–191]. In the CNS endothelium, APC activates protease activated receptor-1 (PAR-1), which elicits protective signaling by enhancing the BBB integrity via Rac1-dependent cytoskeletal stabilization, suppression of cerebrovascular MMP-9 activity, and inhibition of proinflammatory cytokines expression and apoptosis [188,189,192–194].…”

Hypothalamic S1P/S1PR1 axis controls energy homeostasis

“…This receptor is widely expressed, controlling the cellular process in heart, skeletal muscle, colon 14 and other tissues. Although S1P receptors have been identified in the central nervous system 33,34 , the presence and function of S1PR1 specifically in the hypothalamus was not reported. Surprisingly, our study revealed that hypothalamic nuclei are highly enriched with S1PR1 protein levels, when compared with peripheral tissues.…”