TL;DR: The new enhanced NpHR (eNpHR) allows safe, high-level expression in mammalian neurons, without toxicity and with augmented inhibitory function, in vitro and in vivo.
Abstract: Temporally precise inhibition of distinct cell types in the intact nervous system has been enabled by the microbial halorhodopsin NpHR, a fast light-activated electrogenic Cl− pump. While neurons can be optically hyperpolarized and inhibited from firing action potentials at moderate NpHR expression levels, we have encountered challenges with pushing expression to extremely high levels, including apparent intracellular accumulations. We therefore sought to molecularly engineer NpHR to achieve strong expression without these cellular side effects. We found that high expression correlated with endoplasmic reticulum (ER) accumulation, and that under these conditions NpHR colocalized with ER proteins containing the KDEL ER retention sequence. We screened a number of different putative modulators of membrane trafficking and identified a combination of two motifs, an N-terminal signal peptide and a C-terminal ER export sequence, that markedly promoted membrane localization and ER export defined by confocal microscopy and whole-cell patch clamp. The modified NpHR displayed increased peak photocurrent in the absence of aggregations or toxicity, and potent optical inhibition was observed not only in vitro but also in vivo with thalamic single-unit recording. The new enhanced NpHR (eNpHR) allows safe, high-level expression in mammalian neurons, without toxicity and with augmented inhibitory function, in vitro and in vivo.
TL;DR: The results suggest a sequential mode of COPII and COPI action and indicate that the transport complexes are ER-to-Golgi transport intermediates from which COPI may be involved in recycling material to the ER.
TL;DR: Microinjection of anti-COP-I antibodies or expression of a GTP-restricted Arf-1 mutant does not interfere with Golgi-to-ER transport of Shiga toxin/Shiga-like toxin-1 or with the apparent recycling to the ER of GolGi-resident glycosylation enzymes, indicating the existence of at least two distinct pathways for Golgi -to- ER transport, one COP-I dependent and the other COP- I independent.
Abstract: The cytosolic coat-protein complex COP-I interacts with cytoplasmic 'retrieval' signals present in membrane proteins that cycle between the endoplasmic reticulum (ER) and the Golgi complex, and is required for both anterograde and retrograde transport in the secretory pathway. Here we study the role of COP-I in Golgi-to-ER transport of several distinct marker molecules. Microinjection of anti-COP-I antibodies inhibits retrieval of the lectin-like molecule ERGIC-53 and of the KDEL receptor from the Golgi to the ER. Transport to the ER of protein toxins, which contain a sequence that is recognized by the KDEL receptor, is also inhibited. In contrast, microinjection of anti-COP-I antibodies or expression of a GTP-restricted Arf-1 mutant does not interfere with Golgi-to-ER transport of Shiga toxin/Shiga-like toxin-1 or with the apparent recycling to the ER of Golgi-resident glycosylation enzymes. Overexpression of a GDP-restricted mutant of Rab6 blocks transport to the ER of Shiga toxin/Shiga-like toxin-1 and glycosylation enzymes, but not of ERGIC-53, the KDEL receptor or KDEL-containing toxins. These data indicate the existence of at least two distinct pathways for Golgi-to-ER transport, one COP-I dependent and the other COP-I independent. The COP-I-independent pathway is specifically regulated by Rab6 and is used by Golgi glycosylation enzymes and Shiga toxin/Shiga-like toxin-1.
TL;DR: Results indicate moderately slowed GFP diffusion in a continuous ER lumen, presumably within a pre- or cis-Golgi compartment involved in KDEL-substrate retention.
TL;DR: The plant-derived human anti-rabies mAb (mAbP) was as efficient as HRIG for post-exposure prophylaxis against rabies virus in hamsters, indicating that differences in N-glycosylation do not affect the efficacy of the antibody in this model.
Abstract: Plant genetic engineering led to the production of plant-derived mAb (mAbP), which provides a safe and economically feasible alternative to the current methods of antibody production in animal systems. In this study, the heavy and light chains of human anti-rabies mAb were expressed and assembled in planta under the control of two strong constitutive promoters. An alfalfa mosaic virus untranslated leader sequence and Lys-Asp-Glu-Leu (KDEL) endoplasmic reticulum retention signal were linked at the N and C terminus of the heavy chain, respectively. mAbP was as effective at neutralizing the activity of the rabies virus as the mammalian-derived antibody (mAbM) or human rabies Ig (HRIG). The mAbP contained mainly oligomannose type N-glycans (90%) and had no potentially antigenic α(1,3)-linked fucose residues. mAbP had a shorter half-life than mAbM. The mAbP was as efficient as HRIG for post-exposure prophylaxis against rabies virus in hamsters, indicating that differences in N-glycosylation do not affect the efficacy of the antibody in this model.