Overexpression of Shrm4 promotes proliferation and differentiation of neural stem cells through activation of GABA signaling pathway

The Critical Role of the Shroom Family Proteins in Morphogenesis, Organogenesis and Disease

The Shroom (Shrm) family of actin-binding proteins has a unique and highly conserved Apx/Shrm Domain 2 (ASD2) motif. Shroom protein directs the subcellular localization of Rho-associated kinase (ROCK), which remodels the actomyosin cytoskeleton and changes cellular morphology via its ability to phosphorylate and activate non-muscle myosin II. Therefore, the Shrm-ROCK complex is critical for the cellular shape and the development of many tissues, including the neural tube, eye, intestines, heart, and vasculature system. Importantly, the structure and expression of Shrm proteins are also associated with neural tube defects, chronic kidney disease, metastasis of carcinoma, and X-link mental retardation. Therefore, a better understanding of Shrm-mediated signaling transduction pathways is essential for the development of new therapeutic strategies to minimize damage resulting in abnormal Shrm proteins. This paper provides a comprehensive overview of the various Shrm proteins and their roles in morphogenesis and disease.

Effects of overexpression of Hsp70 in neural stem cells on neurotoxicity and cognitive dysfunction in neonatal mice under sevoflurane exposure

As one of the commonly used inhalation anesthetics in clinical practice, sevoflurane is currently widely applied in surgery for children and the elderly due to its safety and efficacy. However, the neurotoxicity and cognitive impairment induced by sevoflurane exposure cannot be ignored. A recombinant adenovirus with green fluorescent protein-labeled heat shock protein 70 (Hsp70) was constructed and used to infect neural stem cells (NSCs) separated from neonatal mice. Quantitative real-time PCR and Western blot assays were used to evaluate the expression of certain genes. 5‑Ethynyl‑2'‑deoxyuridine staining and cell counting kit assay were used to detect the proliferation and differentiation ability of NSCs. The Morris water maze experiment was used to test the cognitive abilities of mice. Adv-Hsp70 induced the overexpression of Hsp70 in mouse NSCs. Upregulation of Hsp70 promoted the proliferation ability and differentiation of mouse NSCs. NSCs that overexpressed Hsp70 attenuated sevoflurane-induced neurotoxicity and protected cognitive dysfunction in mice under sevoflurane exposure. In summary, our findings demonstrate the potential of overexpression of Hsp70 in NSCs against sevoflurane-induced impairments.

Inhibiting PDE7A Enhances the Protective Effects of Neural Stem Cells on Neurodegeneration and Memory Deficits in Sevoflurane-Exposed Mice

Sevoflurane is widely used in general anesthesia, especially for children. However, prolonged exposure to sevoflurane is reported to be associated with adverse effects on the development of brain in infant monkey. Neural stem cells (NSCs), with potent proliferation, differentiation, and renewing ability, provide an encouraging tool for basic research and clinical therapies for neurodegenerative diseases. We aim to explore the functional effects of injecting NSCs with phosphodiesterase 7A (PDE7A) knock-down in infant mice exposed to sevoflurane. The effects of PDE7A in NSCs proliferation and differentiation were determined by cell counting kit-8 (CCK-8) assay and differentiation-related gene expression assay, respectively. The effects of NSCs with modified PDE7A on mice’s long-term memory and learning ability were assessed by behavioral assays. Our data demonstrated that depleting PDE7A promoted, whereas forcing PDE7A suppressed the activation of cAMP/cAMP-response element binding protein (CREB) signaling as well as cell proliferation and neuronal differentiation of NSCs. Inhibition of PDE7A in NSCs exhibited profound improved effects on long-term memory and learning ability of mice exposed to sevoflurane. Our results for the first time show that knock-down of PDE7A improves the neurogenesis of NSCs in vitro and in vivo, and is beneficial for alleviating sevoflurane-induced brain damage in infant mice.

Shrm4 contributes to autophagy inhibition and neuroprotection following ischemic stroke by mediating GABAB receptor activation

Acute ischemic stroke is one of the leading causes of death in developed countries and the most common cause of disability in adults worldwide. Despite advances in the understanding of stroke pathophysiology, therapeutic options remain limited. In this study, we explored the interaction of Shrm4 and the metabotropic gamma-aminobutyric acid (GABA) receptors (GABA_B ) in ischemic stroke. A transient middle cerebral artery occlusion (MCAO) model was induced by filament insertion in Shrm4+/+ and wild-type C57BL/6J mice, followed by reperfusion for up to 7 days. Baclofen was administered was used to activate GABA_B in vivo during reperfusion. Neurological deficits, motor and memory functions, and infarct volume were determined in the various mouse groups. Furthermore, we also developed an oxygen-glucose deprivation (OGD) cell model in primary neurons to test Shrm4/GABA_B interactions in vitro. Shrm4 was observed to decrease infarct volume and neuronal cell loss in penumbra, and rescue neurological deficits in MCAO mice. Notably, Shrm4 also increased pole climbing speed, reduced foot faults, and increased escape latency in the Morris water maze test, while reducing neuron autophagy through an interaction with GABA_B receptors. GABA_B activation using baclofen further reduced OGD-induced neuron damage in culture and stroke outcomes of MCAO, relative to Shrm4 alone. Taken together, Shrm4-mediated GABA_B activation confers neuroprotection by reducing neuronal autophagy in acute ischemic stroke.