Figure 4 | Cell Death & Differentiation

Figure 4

From: The ALS-linked E102Q mutation in Sigma receptor-1 leads to ER stress-mediated defects in protein homeostasis and dysregulation of RNA-binding proteins

Figure 4

mSigR1 leads to structural abnormalities of ER and mitochondria. (a) MCF7 cells expressing pcDNA, wtSigR1 or mSigR1 were fixed with 2.5% buffered glutaraldehyde and processed for EM. Several membrane-bound vacuolar structures (black arrows) probably derived from the ER in a representative mSigR1-expressing cell compared to cells expressing wtSigR1 and pcDNA control. Scale bars, 1 μm. (b) Higher magnification showing the widened ER (arrows in right panel) in representative mSigR1-expressing cells compared to pcDNA and wtSigR1-transfected cells. Scale bar, 0.5 μm. (c) Higher magnification showing double membrane autophagic vacuoles in representative mSigR1-expressing MCF-7 cells. (a) Large autophagosome (AV; arrowheads) containing mitochondria and other structures in close proximity to lysosomes (Lys); (b) autophagosome (arrowhead) and widened ER (white arrow); (c) autophagosome (AV) and lysosomes (Lys). Scale bar, 0.5 μm. (d) Enlarged mitochondria (arrows) showing abnormal cristae architecture, some undergoing mitophagy (arrowheads) in mSigR1-transfected cells. Scale bar, 0.4 μm. (e) Primary lymphoblastoid cells from healthy control and E102Q-SigR1 fALS patients were fixed with 2.5% buffered glutaraldehyde and processed for EM. Control lymphoblasts show an overall normal ultrastructure, whereas E102Q-SigR1 fALS patient lymphoblastoid cells reveal prominent accumulation of autophagic material. Scale bars, 2.5 μm. (f) Prominent nuclear envelope (arrows) protrusions in E102Q-SigR1 fALS lymphoblastoid cells and rather normal nuclear envelope in control lymphoblastoid cells. Scale bar, 0.5 μm. (g) Normal ER (white arrows) and mitochondria (gray arrows) in healthy control lymphoblastoid cells; E102Q-SigR1 fALS patient lymphoblastoid cells showing overall widened ER (arrows). Scale bar, 0.5 μm. (h) E102Q-SigR1 fALS lymphoblasts displaying vacuolar degeneration of mitochondria (gray arrows), multivesicular bodies (arrowheads) and autophagosomes filled with membranous and granular material (white arrows). Black arrow: nuclear envelope protrusion. Scale bars, 0.4 μm

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