The Rab5 effector EEA1 is a core component of endosome docking

Intracellular membrane docking and fusion requires the interplay between soluble factors and SNAREs. The SNARE hypothesis postulates that pairing between a vesicular v-SNARE and a target membrane z-SNARE is the primary molecular interaction underlying the specificity of vesicle targeting as well as lipid bilayer fusion. This proposal is supported by recent studies using a minimal artificial system. However, several observations demonstrate that SNAREs function at multiple transport steps and can pair promiscuously, questioning the role of SNAREs in conveying vesicle targeting. Moreover, other proteins have been shown to be important in membrane docking or tethering. Therefore, if the minimal machinery is defined as the set of proteins sufficient to reproduce in vitro the fidelity of vesicle targeting, docking and fusion as in vivo, then SNAREs are not sufficient to specify vesicle targeting. Endosome fusion also requires cytosolic factors and is regulated by the small GTPase Rab5. Here we show that Rab5-interacting soluble proteins can completely substitute for cytosol in an in vivo endosome-fusion assay, and that the Rab5 effector EEA1 is the only factor necessary to confer minimal fusion activity. Rab5 and other associated proteins seem to act upstream of EEA1, implying that Rab5 effectors comprise both regulatory molecules and mechanical components of the membrane transport machinery. We further show that EEA1 mediates endosome docking and, together with SNAREs, leads to membrane fusion.     

具有三个CM公共值的亚纯函数的唯一性

本文指出仪洪勋和Brosch G在具有三个判别的CM公共值的亚纯函数的唯一性定理中,关于对数函数的导数是整函数的推导,可以用指数函数求导的方法来证明.改进了仪洪勋和Brosch G关于重值与唯一性定理.     

Cloning and characterization of a vasopressin V2 receptor and possible link to nephrogenic diabetes insipidus.

The antidiuretic effect of arginine vasopressin (AVP) is mediated by renal-type (V2) receptors linked to adenylyl cyclase. We report here the cloning of the rat kidney V2 AVP receptor complementary DNA that encodes a 370-amino-acid protein with a transmembrane topography characteristic of G protein-coupled receptors, and with similarity to the V1a (hepatic) AVP receptor in its seven membrane-spanning domains. Expression of the cloned cDNA in mammalian cells showed specific ligand binding and activity characteristic of the native V2 AVP receptor. The receptor messenger RNA is detected only in the kidney. The human V2 receptor gene has been localized to the long arm of the X chromosome close to the locus for nephrogenic diabetes insipidus, an X-linked recessive disorder characterized by renal resistance to the antidiuretic action of AVP.     

Linkage of epidermolytic hyperkeratosis to the type II keratin gene cluster on chromosome 12q.

We investigated the molecular genetics of epidermolytic hyperkeratosis (EHK), a dominant disorder characterized by epidermal blistering, hyperkeratosis, vacuolar degeneration and clumping of keratin filaments. Based on this pathology, we have excluded by linkage analysis several candidate genes for the disease; in contrast, complete linkage was obtained with the type II keratin, K1, on 12q11-q13. Linkage in this region of chromosome 12 was confirmed using several other markers, and multi-locus linkage analyses further supported this location. Keratins are excellent EHK gene candidates since their expression is specific to the suprabasal epidermal layers. In the pedigree studied here, a type II keratin gene, very probably K1, is implicated as the site of the molecular defect causing EHK.     

Re-Os isotopic evidence for a lower crustal origin of massif-type anorthosites

Massif-type anorthosites are large igneous complexes of Proterozoic age. They are almost monomineralic, representing vast accumulations of plagioclase with subordinate pyroxene or olivine and Fe-Ti oxides--the 930-Myr-old Rogaland anorthosite province in southwest Norway represents one of the youngest known expressions of such magmatism. The source of the magma and geodynamic setting of massif-type anorthosites remain long-standing controversies in Precambrian geology, with no consensus existing as to the nature of the parental magmas or whether these magmas primarily originate in the Earth's mantle or crust. At present, massif-type anorthosites are believed to have crystallized from either crustally contaminated mantle-derived melts that have fractionated olivine and pyroxenes at depth or primary aluminous gabbroic to jotunitic melts derived from the lower continental crust. Here we report rhenium and osmium isotopic data from the Rogaland anorthosite province that strongly support a lower crustal source for the parental magmas. There is no evidence of significantly older crust in southwest Scandinavia and models invoking crustal contamination of mantle-derived magmas fail to account for the isotopic data from the Rogaland province. Initial osmium and neodymium isotopic values testify to the melting of mafic source rocks in the lower crust with an age of 1,400-1,550 Myr.     

Pain relief by xenograft of subarachnoid microencapsulated bovine chromaffin cells in cancer patients

The bovine chromaffin cells (BCC) implanted into the subarachnoid space can release analgesic substances such as opioid peptides and ealeeholamines. Clinical trials have provided the evidence that the implantation of polyvinylchloride ( PVC) hollow fiber encapsulated BCC by surgery can relief the pain in cancer patients. In the present study, BCC were encapsulated in alginate-polylysine-alginate (APA) mieroencapsules which protect the grafting of xenogeneic cells from host immune system anil allow BCC to function effectively without using immunosuppression agents. The microencapsulated BCCs (5 X 106~—8 X 106) were transplanted into the subarachnoid space I^._s of 17 patients who suffered from chronic cancer pain and had to have long-term administration of analgesics. The pain scores and morphine intake tesl showed that microencapsulated BCC graft totally stopped the chronic pain in three of the patients over a period of 200 days and in the other three over a period of 100 days. The resulls suggesl thai APA microencapsulated BCC xenotransplantation could be a novel alternative approach to managing pain of cancer patients.     

The patterns and dynamics of genomic instability in metastatic pancreatic cancer

Pancreatic cancer is an aggressive malignancy with a five-year mortality of 97-98%, usually due to widespread metastatic disease. Previous studies indicate that this disease has a complex genomic landscape, with frequent copy number changes and point mutations, but genomic rearrangements have not been characterized in detail. Despite the clinical importance of metastasis, there remain fundamental questions about the clonal structures of metastatic tumours, including phylogenetic relationships among metastases, the scale of ongoing parallel evolution in metastatic and primary sites, and how the tumour disseminates. Here we harness advances in DNA sequencing to annotate genomic rearrangements in 13 patients with pancreatic cancer and explore clonal relationships among metastases. We find that pancreatic cancer acquires rearrangements indicative of telomere dysfunction and abnormal cell-cycle control, namely dysregulated G1-to-S-phase transition with intact G2-M checkpoint. These initiate amplification of cancer genes and occur predominantly in early cancer development rather than the later stages of the disease. Genomic instability frequently persists after cancer dissemination, resulting in ongoing, parallel and even convergent evolution among different metastases. We find evidence that there is genetic heterogeneity among metastasis-initiating cells, that seeding metastasis may require driver mutations beyond those required for primary tumours, and that phylogenetic trees across metastases show organ-specific branches. These data attest to the richness of genetic variation in cancer, brought about by the tandem forces of genomic instability and evolutionary selection.     

Formation of chiral morphologies through selective binding of amino acids to calcite surface steps.

Many living organisms contain biominerals and composites with finely tuned properties, reflecting a remarkable level of control over the nucleation, growth and shape of the constituent crystals. Peptides and proteins play an important role in achieving this control. But the general view that organic molecules affect mineralization through stereochemical recognition, where geometrical and chemical constraints dictate their binding to a mineral, seems difficult to reconcile with a mechanistic understanding, where crystallization is controlled by thermodynamic and kinetic factors. Indeed, traditional crystal growth models emphasize the inhibiting effect of so-called 'modifiers' on surface-step growth, rather than stereochemical matching to newly expressed crystal facets. Here we report in situ atomic force microscope observations and molecular modelling studies of calcite growth in the presence of chiral amino acids that reconcile these two seemingly divergent views. We find that enantiomer-specific binding of the amino acids to those surface-step edges that offer the best geometric and chemical fit changes the step-edge free energies, which in turn results in macroscopic crystal shape modifications. Our results emphasize that the mechanism underlying crystal modification through organic molecules is best understood by considering both stereochemical recognition and the effects of binding on the interfacial energies of the growing crystal.