Evolutionary analysis and molecular dissection of caveola biogenesis

Caveolae are an abundant feature of mammalian cells. Integral membrane proteins called caveolins drive the formation of caveolae but the precise mechanisms underlying caveola formation, and the origin of caveolae and caveolins during evolution, are unknown

Largen: A Molecular Regulator of Mammalian Cell Size Control

Little is known about how mammalian cells maintain cell size homeostasis. We conducted a novel genetic screen to identify cell-size-controlling genes and isolated Largen, the product of a gene (PRR16) that increased cell size upon overexpression in human cells. Invitro evidence indicated that Largen preferentially stimulates the translation of specific subsetsof mRNAs, including those encoding proteins affecting mitochondrial functions. The involvement of Largen in mitochondrial respiration was consistentwith the increased mitochondrial mass and greater ATP production in Largen-overexpressing cells. Furthermore, Largen overexpression led to increased cell size invivo, as revealed by analyses of conditional Largen transgenic mice. Our results establish Largen as an important link between mRNA translation, mitochondrial functions, and the control of mammalian cell size

Urinary Tract Infection Diagnosis and Response to Therapy in Long-Term Care: A Prospective Observational Study

BACKGROUND: The prevalence of asymptomatic bacteriuria among residents of long-term care (LTC) facilities is high, and is a source of inappropriate antibiotic prescription. OBJECTIVE: To establish symptoms and signs associated with a positive urine culture, and to determine whether antibiotic therapy is associated with functional improvement. METHODS: A total of 101 LTC patients were prospectively observed after submission of urine for culture. RESULTS: The culture positivity rate was consistent with the expected asymptomatic bacteriuria rate. Change in mental status and male sex were associated with culture positivity. Treatment decisions were not consistent with culture results. Treatment did not lead to improvement in activities of daily living scores at two days or seven days. DISCUSSION: Significant growth cannot be well predicted based on clinical variables; thus, the decision to submit urine is somewhat arbitrary. Because urine culture testing and treatment does not lead to functional improvement, restricting access to the test may be reasonable. CONCLUSION: Urine culture testing in LTC facilities does not lead to functional improvement

D-2-hydroxyglutarate produced by mutant IDH1 perturbs collagen maturation and basement membrane function

Isocitrate dehydrogenase-1 (IDH1) R132 mutations occur in glioma, but their physiological significance is unknown. Here we describe the generation and characterization of brain-specific Idh1 R132H conditional knockin (KI) mice. Idh1 mutation results in hemorrhage and perinatal lethality. Surprisingly, intracellular reactive oxygen species (ROS) are attenuated in Idh1-KI brain cells despite an apparent increase in the NADP+/NADPH ratio. Idh1-KI cells also show high levels of D-2-hydroxyglutarate (D2HG) that are associated with inhibited prolyl-hydroxylation of hypoxia-inducible transcription factor-1?? (Hif1??) and up-regulated Hif1?? target gene transcription. Intriguingly, D2HG also blocks prolyl-hydroxylation of collagen, causing a defect in collagen protein maturation. An endoplasmic reticulum (ER) stress response induced by the accumulation of immature collagens may account for the embryonic lethality of these mutants. Importantly, D2HG-mediated impairment of collagen maturation also led to basement membrane (BM) aberrations that could play a part in glioma progression. Our study presents strong in vivo evidence that the D2HG produced by the mutant Idh1 enzyme is responsible for the above effects. © 2012 by Cold Spring Harbor Laboratory Press.close71696

Clathrin Triskelia Show Evidence of Molecular Flexibility

The clathrin triskelion, which is a three-legged pinwheel-shaped heteropolymer, is a major component in the protein coats of certain post-Golgi and endocytic vesicles. At low pH, or at physiological pH in the presence of assembly proteins, triskelia will self-assemble to form a closed clathrin cage, or “basket”. Recent static light scattering and dynamic light scattering studies of triskelia in solution showed that an individual triskelion has an intrinsic pucker similar to, but differing from, that inferred from a high resolution cryoEM structure of a triskelion in a clathrin basket. We extend the earlier solution studies by performing small-angle neutron scattering (SANS) experiments on isolated triskelia, allowing us to examine a higher q range than that probed by static light scattering. Results of the SANS measurements are consistent with the light scattering measurements, but show a shoulder in the scattering function at intermediate q values (0.016 Å−1), just beyond the Guinier regime. This feature can be accounted for by Brownian dynamics simulations based on flexible bead-spring models of a triskelion, which generate time-averaged scattering functions. Calculated scattering profiles are in good agreement with the experimental SANS profiles when the persistence length of the assumed semiflexible triskelion is close to that previously estimated from the analysis of electron micrographs