Abstract
As the main organelles for the clearance of damaged proteins and damaged organelles, the function of lysosomes is crucial for maintaining the intracellular homeostasis of long-lived neurons. A stable acidic environment is essential for lysosomes to perform their functions. TMEM175 has been identified as a new K+ channel that is responsible for regulating lysosomal membrane potential and pH stability in neurons. This study aimed to understand the role of TMEM175 in lysosomal function of neurons and neuronal injury following cerebral ischemia-reperfusion (I/R). A middle-cerebral-artery occlusion/reperfusion (MCAO/R) model was established in adult male Sprague-Dawley rats in vivo, and cultured neurons were exposed to oxygen-glucose deprivation/reoxygenation (OGD/R) to mimic ischemia-reperfusion (I/R) injury in vitro. We found that the protein level of TMEM175 decreased after cerebral I/R injury and that TMEM175 overexpression ameliorated MCAO/R-induced brain-cell death and neurobehavioral deficits in vivo. Furthermore, these results were recapitulated in cultured neurons. Acridine orange (AO) staining, as well as LysoSensor Green DND-189, cathepsin-B (CTSB), and cathepsin-D (CTSD) activities, showed that TMEM175 deficiency inhibited the hydrolytic function of lysosomes by affecting lysosomal pH. In contrast, TMEM175 upregulation reversed OGD/R-induced lysosomal dysfunction and impaired mitochondrial accumulation in cultured neurons. TMEM175 deficiency induced by cerebral I/R injury leads to compromised lysosomal pH stability, thus inhibiting the hydrolytic function of lysosomes. Consequently, lysosomal-dependent degradation of damaged mitochondria is suppressed and thereby exacerbates brain damage. Exogenous up-regulation of TMEM175 protein level could reverse the neuronal lysosomal dysfunction after ischemia-reperfusion.
Highlights
Cerebral ischemia is a form of stroke that causes considerable disability and mortality worldwide, which induces a heavy burden to both society and affected families
We investigated the role of Transmembrane protein 175 (TMEM175) loss-of-function mutations on the hydrolytic function of lysosomes in vitro: Acridine orange (AO) staining conducted at 2 h, 4 h after oxygen-glucose deprivation/reoxygenation (OGD/R) treatment and LysoSensor Green DND-189 conducted at 4 h after OGD/R treatment were used to detect changes in lysosomal pH
TMEM175 protein levels are decreased in penumbral tissue after ischemia/reperfusion injury To investigate whether the protein level of TMEM175 changes after middle-cerebral-artery occlusion/reperfusion (MCAO/R), we performed MCAO/R in SD rats, and Western blot analysis of protein samples from penumbral tissue was subsequently performed
Summary
Cerebral ischemia is a form of stroke that causes considerable disability and mortality worldwide, which induces a heavy burden to both society and affected families. A. Reperfusion following focal cerebral ischemia leads to cellular changes, including the accumulation of misfolded proteins and organelle damage; in particular, significant mitochondrial dysfunction occurs, such as mitochondrial permeability-transition-pore opening, mitochondrial morphological damage, Ca2+-induced mitochondrial swelling, and the release of mitochondrial. Mitochondria have been implicated as central players in the development of ischemic cell death, both through impairment of their normal roles in generating ATP for neuronal function and as key mediators in cell-death pathways [5]. Recent studies have shown that mitophagy, a lysosomal degradative pathway, is essential for maintaining neuronal homeostasis via the removal of dysfunctional mitochondria following cerebral ischemia-reperfusion (I/R) injury [6, 7]. The hydrolytic function of lysosomes plays a vital role in neuroprotection against ischemic brain injury
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
