Endoplasmic reticulum chaperone BiP/GRP78 knockdown leads to autophagy and cell death of arginine vasopressin neurons in mice

Abstract

The immunoglobulin heavy chain binding protein (BiP), also referred to as 78-kDa glucose-regulated protein (GRP78), is a pivotal endoplasmic reticulum (ER) chaperone which modulates the unfolded protein response under ER stress. Our previous studies showed that BiP is expressed in arginine vasopressin (AVP) neurons under non-stress conditions and that BiP expression is upregulated in proportion to the increased AVP expression under dehydration. To clarify the role of BiP in AVP neurons, we used a viral approach in combination with shRNA interference for BiP knockdown in mouse AVP neurons. Injection of a recombinant adeno-associated virus equipped with a mouse AVP promoter and BiP shRNA cassette provided specific BiP knockdown in AVP neurons of the supraoptic (SON) and paraventricular nuclei (PVN) in mice. AVP neuron-specific BiP knockdown led to ER stress and AVP neuronal loss in the SON and PVN, resulting in increased urine volume due to lack of AVP secretion. Immunoelectron microscopy of AVP neurons revealed that autophagy was activated through the process of AVP neuronal loss, whereas no obvious features characteristic of apoptosis were observed. Pharmacological inhibition of autophagy by chloroquine exacerbated the AVP neuronal loss due to BiP knockdown, indicating a protective role of autophagy in AVP neurons under ER stress. In summary, our results demonstrate that BiP is essential for the AVP neuron system.

Protein Aggregation in the ER: Calm behind the Storm

“…In vitro , ER-phagy receptor RTN3 has been shown to mediate the degradation of mutant pro-AVP, further supporting the role of ER-phagy in clearing pro-AVP aggregates [ 137 ]. While the activity of autophagy is largely considered cytoprotective, a prolonged activation of autophagy may contribute to neuronal cell death [ 210 , 211 , 212 ]. Many questions remain in this area, most importantly how the ER quality control pathways function together in response to misfolded pro-AVP and why they fail to prevent the accumulation of pro-AVP aggregates in FNDI.…”

Characterization of X- box binding protein 1(XBP1) and BiP functions and investigation their roles in YHV replication in P. monodon

“…It is generally accepted that BiP is an essential chaperone which participates in folding process of membranous and secretory proteins in ER (Munro et al, 1986). Therefore, its depletion by RNAi directly disturbed ER homeostasis which led to shrimp lethality (Li et al, 1991;Park et al, 2017;Kawaguchi et al, 2020). High mortality rate in BiP knockdown shrimp even without YHV infection in figure 6 strongly supported this notion.…”

Rostral Hypothalamic Differentiation With Minimal Exogenous Signals in Human Naive Induced Pluripotent Stem Cells

“…In this study, we clearly demonstrated mutant NPII expression in FNDI-speci c hiPSC-derived AVP neurons. Accumulation of mutant proteins in the ER is implicated in the pathophysiology of many diseases, including FNDI 1,[6][7][8][9][10][11][12][13]47,48 ; therefore, FNDI-speci c hiPSC-derived AVP neurons are a promising human model of ER stress and are a valuable resource for drug development. We plan to analyze characteristic structures, such as the ERAC, which was con rmed in mice by electron microscopy, in FNDI-speci c hiPSC-derived AVP neurons.…”

“…Our previous studies using Cys98stop-knock-in FNDI mouse models [4][5][6][7][8][9][10][11][12][13] , indicated that endoplasmic reticulum (ER) stress caused by the accumulation of mutant proteins in the ER could be associated with FNDI pathology. However, further studies, including the use of human models, are needed to investigate the overall pathological mechanisms of FNDI.…”