Ribonuclease-gold labels chondroitin sulphate in guinea pig basophil granules

Analysis of low abundance membrane-associated proteins from rat pancreatic zymogen granules

Zymogen granules (ZG) are specialized storage organelles in the exocrine pancreas that allow the sorting, packaging, and regulated apical secretion of digestive enzymes. As there is a critical need for further understanding of the key processes in regulated secretion to develop new therapeutic options in medicine, we applied a suborganellar proteomics approach to identify peripheral membrane-associated ZG proteins. We focused on the analysis of a "basic" group (pH range 6.2-11) with about 46 spots among which 44 were identified by tandem mass spectrometry. These spots corresponded to 16 unique proteins, including rat mast cell chymase (RMCP-1) and peptidyl-prolyl cis-trans isomerase B (PpiB; cyclophilin B), an ER-resident protein. To confirm that these proteins were specific to zymogen granules and not contaminants of the preparation, we conducted a series of validation experiments. Immunoblotting of ZG subfractions revealed that chymase and PpiB behaved like bona fide peripheral membrane proteins. Their expression in rat pancreas was regulated by feeding behavior. Ultrastructural and immunofluorescence studies confirmed their ZG localization. Furthermore, a chymase-YFP fusion protein was properly targeted to ZG in pancreatic AR42J cells. Interestingly, for both proteins, proteoglycan-binding properties have been reported. The importance of our findings for sorting and packaging during ZG formation is discussed.

Glucosamine for migraine prophylaxis?

Following a fortuitous observation that migraine headaches ceased in a patient receiving glucosamine therapy for osteoarthritis, a further ten patients with migraine or migraine-like vascular headaches, refractory to established preventive or abortive therapies, have been treated with daily oral glucosamine. After a lag of 4-6 weeks, a substantial reduction in headache frequency and/or intensity has been noted; in some cases, the benefit appears to be dose-dependent. Since glucosamine can be a rate-limiting precursor for mucopolysaccharide synthesis, it is germane to note previous reports that heparin and pentosan polysulfate may have migraine-preventive activity. There is reason to suspect that mast cells are central mediators of the neurogenic inflammation associated with migraine and cluster headaches. The heparin produced by mast cells may function to provide feedback down-regulation of mast cell activation, and exerts a range of other anti-inflammatory effects. We postulate that supplemental glucosamine can boost mast cell heparin synthesis - perhaps correcting a functional heparin deficiency - thereby preventing or ameliorating the neurogenic inflammation that mediates pain in vascular headache. Whether or not this idea has validity, a controlled study of glucosamine for migraine prophylaxis appears to be warranted.