118 research outputs found
Molecular Aspects of Secretory Granule Exocytosis by Neurons and Endocrine Cells
Neuronal communication and endocrine signaling are fundamental for integrating
the function of tissues and cells in the body. Hormones released by endocrine
cells are transported to the target cells through the circulation. By contrast, transmitter
release from neurons occurs at specialized intercellular junctions, the synapses.
Nevertheless, the mechanisms by which signal molecules are synthesized,
stored, and eventually secreted by neurons and endocrine cells are very similar.
Neurons and endocrine cells have in common two different types of secretory
organelles, indicating the presence of two distinct secretory pathways. The synaptic
vesicles of neurons contain excitatory or inhibitory neurotransmitters, whereas the
secretory granules (also referred to as dense core vesicles, because of their electron
dense content) are filled with neuropeptides and amines. In endocrine cells, peptide
hormones and amines predominate in secretory granules. The function and content
of vesicles, which share antigens with synaptic vesicles, are unknown for most
endocrine cells. However, in B cells of the pancreatic islet, these vesicles contain
GABA, which may be involved in intrainsular signaling.'
Exocytosis of both synaptic vesicles and secretory granules is controlled by
cytoplasmic calcium. However, the precise mechanisms of the subsequent steps,
such as docking of vesicles and fusion of their membranes with the plasma membrane,
are still incompletely understood. This contribution summarizes recent observations
that elucidate components in neurons and endocrine cells involved in
exocytosis. Emphasis is put on the intracellular aspects of the release of secretory
granules that recently have been analyzed in detail
Bioinformatic analysis of CaBP/calneuron proteins reveals a family of highly conserved vertebrate Ca2+-binding proteins
Sequential Analysis of Trans-SNARE Formation in Intracellular Membrane Fusion
SM proteins stabilize cis-SNARE complexes leading to a specific preferred topology for trans-SNARE formation
Phosphorylation Provides a Negative Mode of Regulation for the Yeast Rab GTPase Sec4p
The Rab family of Ras-related GTPases are part of a complex signaling circuitry in eukaryotic cells, yet we understand little about the mechanisms that underlie Rab protein participation in such signal transduction networks, or how these networks are integrated at the physiological level. Reversible protein phosphorylation is widely used by cells as a signaling mechanism. Several phospho-Rabs have been identified, however the functional consequences of the modification appear to be diverse and need to be evaluated on an individual basis. In this study we demonstrate a role for phosphorylation as a negative regulatory event for the action of the yeast Rab GTPase Sec4p in regulating polarized growth. Our data suggest that the phosphorylation of the Rab Sec4p prevents interactions with its effector, the exocyst component Sec15p, and that the inhibition may be relieved by a PP2A phosphatase complex containing the regulatory subunit Cdc55p
NDR2-mediated Rabin8 phosphorylation is crucial for ciliogenesis by switching binding specificity from phosphatidylserine to Sec15
Mapping excellence in the geography of science: an approach based on Scopus data
As research becomes an ever more globalized activity, there is growing interest in national and international comparisons of standards and quality in different countries and regions. A sign for this trend is the increasing interest in rankings of universities according to their research performance, both inside but also outside the scientific environment. New methods presented in this paper, enable us to map centers of excellence around the world using programs that are freely available. Based on Scopus data, field-specific excellence can be identified and agglomerated in regions and cities where recently highly cited papers were published. Differences in performance rates can be visualized on the map using colours and sizes of the marks
The exocyst is an effector for Sec4p, targeting secretory vesicles to sites of exocytosis.
Polarized secretion requires proper targeting of secretory vesicles to specific sites on the plasma membrane. Here we report that the exocyst complex plays a key role in vesicle targeting. Sec15p, an exocyst component, can associate with secretory vesicles and interact specifically with the rab GTPase, Sec4p, in its GTP-bound form. A chain of protein-protein interactions leads from Sec4p and Sec15p on the vesicle, through various subunits of the exocyst, to Sec3p, which marks the sites of exocytosis on the plasma membrane. Sec4p may control the assembly of the exocyst. The exocyst may therefore function as a rab effector system for targeted secretion
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