There are functional inter-relationships between the beta cells of the endocrine pancreas and the pineal gland, where the synchronizing circadian molecule melatonin originates. The aim of this study was to elucidate a putative interaction between insulin and melatonin in diabetic patients and a diabetic rat model. We analyzed glucose, insulin, and melatonin levels of type 2 patients, as well as type 2 diabetic Goto Kakizaki (GK) rats by radioimmunoassay. Expression of pancreatic melatonin and pineal insulin receptors, as well as arylalkylamine-N-acetyltransferase (AANAT), was determined by real-time reverse transcriptase polymerase chain reaction (RT-PCR). The AANAT enzyme activity was measured in pineal homogenates. Diabetic patients showed a decrease in melatonin levels, while in the pancreas of GK rats an upregulation of the melatonin-receptor mRNA was determined. The pancreatic islets of GK rats showed expression of the mRNA for the pancreatic melatonin (MT1) receptor, which had previously been identified in rats and insulinoma (INS1) cells. Besides their presence in animal cells, the MT1-receptor transcript was also detected in human pancreas by RT-PCR. Whereas the rat pancreatic mRNA expression of the MT1-receptor was significantly increased, the activity of the pineal AANAT enzyme was reduced. The latter observation was in accordance with plasma melatonin levels. The insulin-receptor mRNA of the pineal gland was found to be reduced in GK rats. Our observations suggest a functional inter-relationship between melatonin and insulin, and may indicate a reduction of melatonin in the genesis of diabetes.

Synaptic transmission relies on effective and accurate compensatory endocytosis. F-BAR proteins may serve as membrane curvature sensors and/or inducers and thereby support membrane remodelling processes; yet, their in vivo functions urgently await disclosure. We demonstrate that the F-BAR protein syndapin I is crucial for proper brain function. Syndapin I knockout (KO) mice suffer from seizures, a phenotype consistent with excessive hippocampal network activity. Loss of syndapin I causes defects in presynaptic membrane trafficking processes, which are especially evident under high-capacity retrieval conditions, accumulation of endocytic intermediates, loss of synaptic vesicle (SV) size control, impaired activity-dependent SV retrieval and defective synaptic activity. Detailed molecular analyses demonstrate that syndapin I plays an important role in the recruitment of all dynamin isoforms, central players in vesicle fission reactions, to the membrane. Consistently, syndapin I KO mice share phenotypes with dynamin I KO mice, whereas their seizure phenotype is very reminiscent of fitful mice expressing a mutant dynamin. Thus, syndapin I acts as pivotal membrane anchoring factor for dynamins during regeneration of SVs. The EMBO Journal (2011) 30, 4955-4969. doi: 10.1038/emboj.2011.339; Published online 16 September 201

Vision is a highly rhythmic function adapted to the extensive changes in light intensity occurring over the 24-hour day. This adaptation relies on rhythms in cellular and molecular processes, which are orchestrated by a network of circadian clocks located within the retina and in the eye, synchronized to the day/night cycle and which, together, fine-tune detection and processing of light information over the 24-hour period and ensure retinal homeostasis. Systematic or high throughput studies revealed a series of genes rhythmically expressed in the retina, pointing at specific functions or pathways under circadian control. Conversely, knockout studies demonstrated that the circadian clock regulates retinal processing of light information. In addition, recent data revealed that it also plays a role in development as well as in aging of the retina. Regarding synchronization by the light/dark cycle, the retina displays the unique property of bringing together light sensitivity, clock machinery, and a wide range of rhythmic outputs. Melatonin and dopamine play a particular role in this system, being both outputs and inputs for clocks. The retinal cellular complexity suggests that mechanisms of regulation by light are diverse and intricate. In the context of the whole eye, the retina looks like a major determinant of phase resetting for other tissues such as the retinal pigmented epithelium or cornea. Understanding the pathways linking the cell-specific molecular machineries to their cognate outputs will be one of the major challenges for the future.

Two stage specific cell-wall lytic enzymes (autolysins) from different strains of the unicellular, biflagellated green alga Chlamydomonas reinhardtii were isolated and purified to homogeneity. Quantitative and specific photometric assays for biological activity were worked out to follow fractionation and to establish lytic specificity and kinetics. The autolysins were studied for enzymatic properties and screened for biological activity towards several wall components obtained by salt extractions of sporangia and zoospores from C. reinhardtii. The autolysins are proteolytic enzymes, fragmenting proline-or hydroxyproline-containing polypeptides in structures like connective tissue. They attack predominantly selected domains within the walls of zoosporangia or gametes. The sporangial autolysins are not only site-and strain-specific but also stage-specific, whereas the gamete autolysins lyse cell walls of gametes as well as those of sporangia and zoospores.Lysis of cell walls is an essential event in the course of life of higher and lower plants [l]. It is the precondition for germination, growth, differentiation, fertilization and conjugation. In the vegetative and sexual cycles of the unicellular flagellated chlorophyte Chlamydomonas reinhardtii there are three stages in which cell wall lysis by the action of lytic enzymes (autolysins) occurs: (a) a sporangial autolysin releases the zoospores from the maternal sporangium; (b) a gamete autolysin dissolves the cell wall of the gamete prior to fusion; (c) an as-yet-unidentified autolysin opens the zygospores when the products of meiosis hatch. The autolysins involved in the first two processes seem to be extraordinarily specific. According to Schlosser [2], they are (a) strain-specific, i.e. they discriminate between cells of different strains of the genus Chlamydomonas; (b) stage-specific, i.e. they recognize the developmental stage of the algae. The sporangial autolysin dissolves only the wall of sporangia; the gamete autolysin acts on the walls of gametes, zoospores and sporangia as well.The gamete autolysin is secreted during agglutination of mating-type plus (mt') and minus (mt-) gametes. It is particularly interesting, because it produces protoplasts from zoospores [3]. It son of the two autolytic systems at the enzyme and the substrate level should provide a better insight into the mechanism of wall lysis, may explain the strain and stage specificity and should help to unravel the complicated composition of algal cell walls.We describe here the isolation and characterization of the sporangial autolysins from two cross-reacting strains of C. reinhardtii and the gamete autolysin of the same splitting group [2]. To follow purification and for enzyme kinetic studies, we have developed quantitative methods for the sporangial and gamete autolysin based on the liberation of wall fragments and protoplasts, respectively. Crude extracts and the purified autolysins were assayed for their hydrolytic activity towards synthetic substrates in order to characterize enzymat...

Previous studies have shown that retinal melatonin plays an important role in the regulation of retinal daily and circadian rhythms. Melatonin exerts its influence by binding to G-protein coupled receptors named melatonin receptor type 1 and type 2 and both receptors are present in the mouse retina. Earlier studies have shown that clock genes are rhythmically expressed in the mouse retina and melatonin signaling may be implicated in the modulation of clock gene expression in this tissue. In this study we determined the daily and circadian expression patterns of Per1, Per2, Bmal1, Dbp, Nampt and c-fos in the retina and in the photoreceptor layer (using laser capture microdissection) in C3H-f+/+ and in melatonin receptors of knockout (MT1 and MT2) of the same genetic background using real-time quantitative RT-PCR. Our data indicated that clock and clock-controlled genes are rhythmically expressed in the retina and in the photoreceptor layer. Removal of melatonin signaling significantly affected the pattern of expression in the retina whereas in the photoreceptor layer only the Bmal1 circadian pattern of expression was affected by melatonin signaling removal. In conclusion, our data further support the notion that melatonin signaling may be important for the regulation of clock gene expression in the inner or ganglion cells layer, but not in photoreceptors.