Physiological modulation of BiP activity by trans-protomer engagement of the interdomain linker.

DnaK/Hsp70 chaperones form oligomers of poorly understood structure and functional significance. Site-specific proteolysis and crosslinking were used to probe the architecture of oligomers formed by the endoplasmic reticulum (ER) Hsp70, BiP. These were found to consist of adjacent protomers engaging the interdomain linker of one molecule in the substrate binding site of another, attenuating the chaperone function of oligomeric BiP. Native gel electrophoresis revealed a rapidly-modulated reciprocal relationship between the burden of unfolded proteins and BiP oligomers and slower equilibration between oligomers and inactive, covalently-modified BiP. Lumenal ER calcium depletion caused rapid oligomerization of mammalian BiP and a coincidental diminution in substrate binding, pointing to the relative inertness of the oligomers. Thus, equilibration between inactive oligomers and active monomeric BiP is poised to buffer fluctuations in ER unfolded protein load on a rapid timescale attainable neither by inter-conversion of active and covalently-modified BiP nor by the conventional unfolded protein response.Supported by grants from the Wellcome Trust (Wellcome 084812/Z/08/Z) the European Commission (EU FP7 Beta-Bat No: 277713), a Wellcome Trust Strategic Award for core facilities to the Cambridge Institute for Medical Research (Wellcome 100140) and a US Public Health Service grant NIH-GM54068 (to LH). DR is a Wellcome Trust Principal Research Fellow.This is the final version of the article. It first appeared from eLife via http://dx.doi.org/10.7554/eLife.0896

Expression of the Na(+)/l(- )symporter (NIS) is markedly decreased or absent in gastric cancer and intestinal metaplastic mucosa of Barrett esophagus

BACKGROUND: The sodium/iodide symporter (NIS) is a plasma membrane glycoprotein that mediates iodide (I(-)) transport in the thyroid, lactating breast, salivary glands, and stomach. Whereas NIS expression and regulation have been extensively investigated in healthy and neoplastic thyroid and breast tissues, little is known about NIS expression and function along the healthy and diseased gastrointestinal tract. METHODS: Thus, we investigated NIS expression by immunohistochemical analysis in 155 gastrointestinal tissue samples and by immunoblot analysis in 17 gastric tumors from 83 patients. RESULTS: Regarding the healthy Gl tract, we observed NIS expression exclusively in the basolateral region of the gastric mucin-producing epithelial cells. In gastritis, positive NIS staining was observed in these cells both in the presence and absence of Helicobacter pylori. Significantly, NIS expression was absent in gastric cancer, independently of its histological type. Only focal faint NIS expression was detected in the direct vicinity of gastric tumors, i.e., in the histologically intact mucosa, the expression becoming gradually stronger and linear farther away from the tumor. Barrett mucosa with junctional and fundic-type columnar metaplasia displayed positive NIS staining, whereas Barrett mucosa with intestinal metaplasia was negative. NIS staining was also absent in intestinalized gastric polyps. CONCLUSION: That NIS expression is markedly decreased or absent in case of intestinalization or malignant transformation of the gastric mucosa suggests that NIS may prove to be a significant tumor marker in the diagnosis and prognosis of gastric malignancies and also precancerous lesions such as Barrett mucosa, thus extending the medical significance of NIS beyond thyroid disease

Electron microscopy of the pancreatic islets stimulated by insulin antibody

Mice were maintained hyperglycemic by daily intraperitoneal injections of immunoglobulins from guinea pigs highly immunized with beef insulin. Hyperglycemic and control mice were killed throughout a period of 3 weeks. Inflammatory infiltrations around the islets were minimal The stimulated beta cells remained heavily degranulated throughout the period of injections. Insignificant changes were seen on the cytomembrane of the beta cell facing the capillary during the initial period of rapid degranulation and thereafter. The density of the rough endoplasmic reticulum increased progressively. The Golgi complexes expanded and became more elaborate. The mitochondria enlarged. Evidence for the continuous elaboration of secretory granules in the Golgi area and for the existence of an immature pregranule in the formation cycle of the secretory granule was obtained in both normal and hyperglycemic animals. Regressive changes in the cells of the islets were absent. </jats:p

Electron Microscopy of the Pancreatic Islets of the Rat: Effects of Prolonged Insulin Injections

The electron microscopical changes of the pancreatic islets of rats were studied during the phase of transient diabetes and during recovery, following a prolonged period of insulin injections. The most characteristic changes, besides the severe degranulation of the beta cells, were the “inactivity” of the Golgi complex and the absence of special spheroidal bodies from its vicinity. Evidence is presented that these satellite bodies may represent pregranules. Differences in the formation of granules in the Golgi area of the alpha, beta and acinar cell are illustrated and discussed.</jats:p