In this task, you are given an abstract of article. Your task is to generate title for this article. Preferred titles are under thirty words.
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Question: The human cytomegalovirus gene product US11 causes rapid degradation of class I major histocompatibility complex (MHCI) heavy chains by inducing their dislocation from the endoplasmic reticulum (ER) and subsequent degradation by the proteasome. This set of reactions resembles the endogenous cellular quality control pathway that removes misfolded or unassembled proteins from the ER. We show that the transmembrane domain (TMD) of US11 is essential for MHCI heavy chain dislocation, but dispensable for MHCI binding. A Gln residue at position 192 in the US11 TMD is crucial for the ubiquitination and degradation of MHCI heavy chains. Cells that express US11 TMD mutants allow formation of MHCI-beta2m complexes, but their rate of egress from the ER is significantly impaired. Further mutagenesis data are consistent with the presence of an alpha-helical structure in the US11 TMD essential for MHCI heavy chain dislocation. The failure of US11 TMD mutants to catalyze dislocation is a unique instance in which a polar residue in the TMD of a type I membrane protein is required for that protein's function. Targeting of MHCI heavy chains for dislocation by US11 thus requires the formation of interhelical hydrogen bonds within the ER membrane.

Answer: Dislocation of a type I membrane protein requires interactions between membrane-spanning segments within the lipid bilayer.

Question: RATIONALE Donor mesenchymal stromal/stem cell (MSC) expansion and fibrotic differentiation is associated with development of bronchiolitis obliterans syndrome (BOS) in human lung allografts. However, the regulators of fibrotic differentiation of these resident mesenchymal cells are not well understood.
OBJECTIVES This study examines the role of endogenous and exogenous prostaglandin (PG)E2 as a modulator of fibrotic differentiation of human lung allograft-derived MSCs.
METHODS Effect of PGE2 on proliferation, collagen secretion, and -smooth muscle actin (-SMA) expression was assessed in lung-resident MSCs (LR-MSCs) derived from patients with and without BOS. The response pathway involved was elucidated by use of specific agonists and antagonists.
MEASUREMENT AND MAIN RESULTS PGE2 treatment of LR-MSCs derived from normal lung allografts significantly inhibited their proliferation, collagen secretion, and -SMA expression. On the basis of pharmacologic and small-interfering RNA approaches, a PGE2/E prostanoid (EP)2/adenylate cyclase pathway was implicated in these suppressive effects. Stimulation of endogenous PGE2 secretion by IL-1 was associated with amelioration of their myofibroblast differentiation in vitro, whereas its inhibition by indomethacin augmented -SMA expression. LR-MSCs from patients with BOS secreted significantly less PGE2 than non-BOS LR-MSCs. Furthermore, BOS LR-MSCs were found to be defective in their ability to induce cyclooxygenase-2, and therefore unable to up-regulate PGE2 synthesis in response to IL-1. BOS LR-MSCs also demonstrated resistance to the inhibitory actions of PGE2 in association with a reduction in the EP2/EP1 ratio.
CONCLUSIONS These data identify the PGE2 axis as an important autocrine-paracrine brake on fibrotic differentiation of LR-MSCs, a failure of which is associated with BOS.

Answer: Prostaglandin E2 as an inhibitory modulator of fibrogenesis in human lung allografts.

Question: Two broad categories of extracellular vesicles (EVs), exosomes and shed microvesicles (sMVs), which differ in size distribution as well as protein and RNA profiles, have been described. EVs are known to play key roles in cell-cell communication, acting proximally as well as systemically. This Review discusses the nature of EV subtypes, strategies for isolating EVs from both cell-culture media and body fluids, and procedures for quantifying EVs. We also discuss proteins selectively enriched in exosomes and sMVs that have the potential for use as markers to discriminate between EV subtypes, as well as various applications of EVs in clinical diagnosis.

Answer:
Extracellular vesicle isolation and characterization: toward clinical application.