Single-dose netupitant/palonosetron versus 3-day aprepitant for preventing chemotherapy-induced nausea and vomiting: a pooled analysis.

Aim: In the absence of comparative studies, guidelines consider neurokinin 1 receptor antagonists (RAs) as interchangeable. We evaluated the pooled efficacy from three cisplatin registration trials, each with arms containing netupitant/palonosetron (NEPA), a fixed neurokinin 1 RA (netupitant)/serotonin Type 3 (5-HT3) RA (palonosetron) combination, and an aprepitant (APR) regimen. Materials & methods: Efficacy data were pooled for rates of complete response (CR: no emesis/no rescue medication), complete protection (CR + no significant nausea), total control (CR + no nausea) and no significant nausea during acute (0-24 h), delayed (>24-120 h) and overall (0-120 h) phases post chemotherapy. Results: Among 621 NEPA and 576 APR patients, response rates were similar for the acute phase, and generally favored NEPA during delayed and overall phases. CR rates for NEPA versus APR were 88.4 versus 89.2%, 81.8 versus 76.9% (p < 0.05) and 78.4 versus 75.0% during the acute, delayed and overall phases, respectively. Conclusion: Oral NEPA administered on day 1 was more effective than a 3-day APR regimen in preventing delayed nausea and vomiting associated with cisplatin.

Lay abstract Oral netupitant/palonosetron (NEPA) is an innovative product that combines two drugs (netupitant and palonosetron) in a single capsule to prevent nausea and vomiting associated with certain types of chemotherapy. In this paper we pooled together the results of three studies comparing the efficacy of NEPA to two drugs from the same classes administered separately (aprepitant regimen) in patients with various solid tumors receiving cisplatin, a type of chemotherapy with a high likelihood of causing nausea and vomiting. In summary, NEPA was more effective than the aprepitant regimen in preventing nausea and vomiting in the later days (days 3­5) following chemotherapy.

Cyclosporine blocks incorporation of HIV-1 envelope glycoprotein into virions.

Cyclosporine (CsA) decreases HIV-1 infectivity by blocking HIV-1 capsid (CA) interaction with target cell cyclophilin A (CypA). Yet, HIV-1 virions produced in the presence of CsA also exhibit decreased infectivity that was previously shown to be independent of the well-characterized HIV-1 CA-CypA interaction. Here, we demonstrate that CsA decreases gp120 and gp41 incorporation into HIV-1 virions and that the fusion of these virions with susceptible target cells is impaired. This effect was not observed with HIV-1 virions pseudotyped with the vesicular stomatitis virus glycoprotein or with the amphotropic envelope protein of murine leukemia virus. It was independent of calcineurin signaling, the endoplasmic reticulum luminal protein cyclophilin B, and the long cytoplasmic tail of gp41. Thus, cyclosporine blocks HIV-1 infectivity via two independent mechanisms, the first involving HIV-1 CA in target cells and the second involving HIV-1 Env in producer cells.

An invariant surface patch on the TRIM5alpha PRYSPRY domain is required for retroviral restriction but dispensable for capsid binding.

TRIM5alpha is a retrovirus restriction factor in the host cell cytoplasm that blocks infection before provirus establishment. Restriction activity requires capsid (CA)-specific recognition by the PRYSPRY domain of TRIM5alpha. To better understand the restriction mechanism, nine charge-cluster-to-triple-alanine mutants in the TRIM5alpha PRYSPRY domain were assessed for CA-specific restriction activity. Five mutants distributed along the TRIM5alpha PRYSPRY primary sequence disrupted restriction activity against N-tropic murine leukemia virus and equine infectious anemia virus. Modeling of the TRIM5alpha PRYSPRY domain based on the crystal structures of PRYSPRY-19q13.4.1, GUSTAVUS, and TRIM21 identified a surface patch where disruptive mutants clustered. All mutants in this patch retained CA-binding activity, a reticular distribution in the cytoplasm, and steady-state protein levels comparable to those of the wild type. Residues in the essential patch are conserved in TRIM5alpha orthologues and in closely related paralogues. The same surface patch in the TRIM18 and TRIM20 PRYSPRY domains is the site of mutants causing Opitz syndrome and familial Mediterranean fever. These results indicate that, in addition to CA-specific binding, the PRYSPRY domain possesses a second function, possibly binding of a cofactor, that is essential for retroviral restriction activity by TRIM5alpha.

Segregation and rapid turnover of EDEM1 by an autophagy-like mechanism modulates standard ERAD and folding activities.

EDEM1 is a crucial regulator of endoplasmic reticulum (ER)-associated degradation (ERAD) that extracts non-native glycopolypeptides from the calnexin chaperone system. Under normal growth conditions, the intralumenal level of EDEM1 must be low to prevent premature interruption of ongoing folding programs. We report that in unstressed cells, EDEM1 is segregated from the bulk ER into LC3-I-coated vesicles and is rapidly degraded. The rapid turnover of EDEM1 is regulated by a novel mechanism that shows similarities but is clearly distinct from macroautophagy. Cells with defective EDEM1 turnover contain unphysiologically high levels of EDEM1, show enhanced ERAD activity and are characterized by impaired capacity to efficiently complete maturation of model glycopolypeptides. We define as ERAD tuning the mechanisms operating in the mammalian ER at steady state to offer kinetic advantage to folding over disposal of unstructured nascent chains by selective and rapid degradation of ERAD regulators.

Glycoprotein folding and the role of EDEM1, EDEM2 and EDEM3 in degradation of folding-defective glycoproteins.

Proteins synthesized in the endoplasmic reticulum (ER) lumen are exposed to several dedicated chaperones and folding factors that ensure efficient maturation. Nevertheless, protein folding remains error-prone and mutations in the polypeptide sequence may significantly reduce folding-efficiency. Folding-incompetent proteins carrying N-glycans are extracted from futile folding cycles in the calnexin chaperone system upon intervention of EDEM1, EDEM2 and EDEM3, three ER-stress-induced members of the glycosyl hydrolase 47 family. This review describes current knowledge about mechanisms regulating folding and disposal of glycoproteins.

EDEM1 regulates ER-associated degradation by accelerating de-mannosylation of folding-defective polypeptides and by inhibiting their covalent aggregation.

Proteins expressed in the endoplasmic reticulum (ER) are covalently modified by co-translational addition of pre-assembled core glycans (glucose(3)-mannose(9)-N-acetylglucosamine(2)) to asparagines in Asn-X-Ser/Thr motifs. N-Glycan processing is essential for protein quality control in the ER. Cleavages and re-additions of the innermost glucose residue prolong folding attempts in the calnexin cycle. Progressive loss of mannoses is a symptom of long retention in the ER and elicits preparation of terminally misfolded polypeptides for dislocation into the cytosol and proteasome-mediated degradation. The ER stress-induced protein EDEM1 regulates disposal of folding-defective glycoproteins and has been described as a mannose-binding lectin. Here we show that elevation of the intralumenal concentration of EDEM1 accelerates ER-associated degradation (ERAD) by accelerating de-mannosylation of terminally misfolded glycoproteins and by inhibiting formation of covalent aggregates upon release of terminally misfolded ERAD candidates from calnexin. Acceleration of Man(9) or Man(5)N-glycans dismantling upon overexpression was fully blocked by substitution in EDEM1 of one catalytic residue conserved amongst alpha1,2-mannosidases, thus suggesting that EDEM1 is an active mannosidase. This mutation did not affect the chaperone function of EDEM1.

A novel stress-induced EDEM variant regulating endoplasmic reticulum-associated glycoprotein degradation.

Proteins expressed in the endoplasmic reticulum (ER) are subjected to a tight quality control. Persistent association with ER-resident molecular chaperones prevents exit of misfolded or incompletely assembled polypeptides from the ER and forward transport along the secretory line. ER-associated degradation (ERAD) is in place to avoid ER constipation. Folding-incompetent products have to be identified to interrupt futile folding attempts and then targeted for unfolding and dislocation into the cytosol for proteasome-mediated destruction. These processes are better understood for N-glycosylated proteins that represent the majority of polypeptides expressed in the ER. EDEM, a mannosidase-like chaperone, regulates the extraction of misfolded glycoproteins from the calnexin cycle. Here we identify and characterize EDEM2, a novel, stress-regulated mannosidase-like protein that operates in the ER lumen. We show that transcriptional up-regulation of EDEM2 depends on the ER stress-activated transcription factor Xbp1, that EDEM2 up-regulation selectively accelerates ERAD of terminally misfolded glycoproteins by facilitating their extraction from the calnexin cycle, and that the previously characterized homolog EDEM is also a soluble protein of the ER lumen in HEK293 cells.

Analyzing folding and degradation of metabolically labelled polypeptides by conventional and diagonal sodium dodecyl sulfate-polyacrylamide gel electrophoresis.

Efficient protein folding and quality control are essential for unperturbed cell viability. Defects in these processes may lead to production of aberrant polypeptides that are either degraded leading to "loss-of-function" phenotypes, or deposited in or outside cells leading to "gain-of-toxic-function" phenotypes. Elucidation of molecular mechanisms regulating folding and quality control of newly synthesized polypeptides is therefore of greatest interest. Here we describe protocols for metabolic labelling of transfected/infected mammalian cells with [(35)S]-methionine and [(35)S]-cysteine, for immunoisolation from detergent extracts of the selected model proteins and for the investigation of the model polypeptide's intracellular fate in response to chaperone-deletions or to cell exposure to folding or degradation inhibitors.