Differential distribution and regulation of expression of synaptosomal-associated protein of 25 kDa isoforms in the Xenopus pituitary gland and brain.

Synaptosomal-associated protein of 25 kDa (SNAP-25) regulates various membrane fusion processes including exocytosis by endocrine and neural cells. To increase our understanding of the occurrence and regulation of SNAP-25 isoforms, we identified and characterized SNAP-25a and SNAP-25b mRNAs in the pituitary gland and brain of the amphibian Xenopus laevis. The proteins are strongly conserved and are resistant to botulinum neurotoxin A but not to botulinum neurotoxin E, as shown by Western blotting.

Alpha-melanophore-stimulating hormone in the brain, cranial placode derivatives, and retina of Xenopus laevis during development in relation to background adaptation.

The amphibian Xenopus laevis can adapt the color of its skin to the light intensity of the background. A key peptide in this adaptation process is alpha-melanophore-stimulating hormone (alpha-MSH), which is derived from proopiomelanocortin (POMC) and released by the endocrine melanotrope cells in the pituitary pars intermedia. In this study, the presence of alpha-MSH in the brain, cranial placode derivatives, and retina of developing Xenopus laevis was investigated using immunocytochemistry, to test the hypothesis that POMC peptide-producing neurons and endocrine cells have a common embryonic origin and a common function, i.

Dynamics and plasticity of peptidergic control centres in the retino-brain-pituitary system of Xenopus laevis.

This review deals particularly with the recent literature on the structural and functional aspects of the retino-brain-pituitary system that controls the physiological process of background adaptation in the aquatic toad Xenopus laevis. Taking together the large amount of multidisciplinary data, a consistent picture emerges of a highly plastic system that efficiently responds to changes in the environmental light condition by releasing POMC-derived peptides, such as the peptide alpha-melanophore-stimulating hormone (alpha-MSH), into the circulation. This plasticity is exhibited by both the central nervous system and the pituitary pars intermedia, at the level of molecules, subcellular structures, synapses, and cells.

Localization and physiological regulation of the exocytosis protein SNAP-25 in the brain and pituitary gland of Xenopus laevis.

In mammals, the synaptosomal-associated protein of 25 kDa, SNAP-25, is generally thought to play a role in synaptic exocytosis of neuronal messengers. Using a polyclonal antiserum against rat SNAP-25, we have shown the presence of a SNAP-25-like protein in the brain of the South-African clawed toad Xenopus laevis by Western blotting and immunocytochemistry. Xenopus SNAP-25 is ubiquitously present throughout the brain, where its distribution in various identified neuronal perikarya and axon tracts is described.

Co-expression in Xenopus neurons and neuroendocrine cells of messenger RNA homologues of exocytosis proteins DOC2 and munc18-1.

The proteins munc18-1 and DOC2 are assumed to play a role in docking of synaptic vesicles in neurotransmitter exocytosis at the presynaptic junction. As the proteins are known to interact, they should co-exist within neurons. We have tested this hypothesis for exocytosis of both classical and peptidergic messengers, by investigating the distribution of the messenger RNAs of munc 18-1 and DOC2 homologues in the brain and pituitary gland of the clawed toad Xenopus laevis, using in situ hybridization.