Pathological transition as the arising mechanism for drug resistance in lung cancer

Despite the tremendous efforts for improving therapeutics of lung cancer patients,its prognosis remains disappoint-ing.This can be largely attributed to the lack of comprehensive understanding of drug resistance leading to insuf-ficient development of effective therapeutics in clinic.Based on the current progresses of lung cancer research,we classify drug resistance mechanisms into three different levels:molecular,cellular and pathological level.All these three levels have significantly contributed to the acquisition and evolution of drug resistance in clinic.Our under-standing on drug resistance mechanisms has begun to change the way of clinical practice and improve patient prognosis.In this review,we focus on discussing the pathological changes linking to drug resistance as this has been largely overlooked in the past decades.

The structural basis for glycerol permeation by human AQP7

Human glycerol channel aquaporin 7(AQP7)conducts glycerol release from adipocyte and enters the cells in pancreatic islets,muscles,and kidney tubules,and thus regulates glycerol metabolism in those tissues.Compared with other human aquaglyceroporins,AQP7 shows a less conserved‘‘NPA”motif in the center cavity and a pair of aromatic residues at Ar/R selectivity filter.To understand the structural basis for the glycerol conductance,we crystallized the human AQP7 and determined the structure at 3.7Å.A substrate binding pocket was found near the Ar/R filter where a glycerol molecule is bound and stabilized by R229.Glycerol uptake assay on human AQP7 as well as AQP3 and AQP10 demonstrated strong glycerol transportation activities at the physiological condition.The human AQP7 structure,in combination with the molecular dynamics simulation thereon,reveals a fully closed conformation with its permeation pathway strictly confined by the Ar/R filter at the exoplasmic side and the gate at the cytoplasmic side,and the binding of glycerol at the Ar/R filter plays a critical role in controlling the glycerol flux by driving the dislocation of the residues at narrowest parts of glycerol pathway in AQP7.

Ribosome biogenesis gene DEF/UTP25 is essential for liver homeostasis and regeneration

Hepatocytes are responsible for diverse metabolic activities in a liver. Proper ribosome biogenesis is essential to sustain the function of hepatocytes. There are approximately 200 factors involved in ribosome biogenesis;however, few studies have focused on the role of these factors in maintaining liver homeostasis. The digestive organ expansion factor(def) gene encodes a nucleolar protein Def that participates in ribosome biogenesis. In addition, Def forms a complex with cysteine protease Calpain3(Capn3) and recruits Capn3 to the nucleolus to cleave protein targets. However, the function of Def has not been characterized in the mammalian digestive organs. In this report, we show that conditional knockout of the mouse def gene in hepatocytes causes cell morphology abnormality and constant infiltration of inflammatory cells in the liver. As age increases, the def conditional knockout liver displays multiple tissue damage foci and biliary hyperplasia. Moreover, partial hepatectomy leads to sudden acute death to the def conditional knockout mice and this phenotype is rescued by intragastric injection of the anti-inflammation drug dexamethasone one day before hepatectomy. Our results demonstrate that Def is essential for maintaining the liver homeostasis and liver regeneration capacity in mammals.

Crystal structure of a bacterial homolog to human lysosomal transporter,spinster

Lysosomes break down various biomolecules and spinster is one of the major efflux carriers removing degradation products from lysosomal lumen to keep it in healthy size and proper function.Although it is well established that a dysfunctional spinster will cause enlarged lysosomes and in turn lead to developmental defects and abnormal behavior in animals,little was known about the transportation mechanism and substrate specificity of spinster.Here,we report a crystal structure of spinster homolog from Hyphomonas neptunium,HnSPNS,in its inward-facing conformation with and without substrate bound.HnSPNS is crystallized in a monomer and a substrate-binding cavity was formed in the center of its transmembrane helices.A blob of electron density corresponding to its substrate was found in the cavity near a conserved residue,R42,which is locked in position by the interactions with conserved residues E129 and R122.Our results suggest that human spinster serves as a transporter translocating negativelycharged lipophilic small molecules and E129 might serve as a switch to control the conformational change via its protonation-deprotonation cycle.