scholarly journals Endophilin-A controls recruitment, priming and fusion of neurosecretory vesicles

2019 ◽  
Author(s):  
Sindhuja Gowrisankaran ◽  
Vicky Steubler ◽  
Sébastien Houy ◽  
Johanna G. Peña del Castillo ◽  
Monika Gelker ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Chromaffin Cells ◽  
Sh3 Domain ◽  
Membrane Curvature ◽  
List Type ◽  
Secretory Vesicles ◽  
Curvature Sensing ◽  
Vesicle Pools ◽  
Endocytic Traffic ◽  
Efficient Distribution

SUMMARYEndophilins-A are conserved endocytic adaptors with membrane curvature-sensing and - inducing properties. We show here that, independently of their role in endocytosis, endophilin-A1 and endophilin-A2 regulate exocytosis of neurosecretory vesicles. The number of neurosecretory vesicles was not altered in chromaffin cells without endophilin, yet fast capacitance and amperometry measurements revealed reduced exocytosis, smaller vesicle pools and changed fusion kinetics. Both endophilin-A1 (brain-enriched) and A2 (ubiquitous) rescued exocytic defects, but endophilin-A2 was more efficient. Distribution of neurosecretory vesicles was altered in the plasma membrane proximity, but levels and distributions of main exocytic and endocytic factors were unchanged, and slow compensatory endocytosis was not robustly affected. Endophilin’s role in exocytosis is mediated through its SH3-domain and, at least in part, interaction with intersectin, a coordinator of exocytic and endocytic traffic. Altogether, we report that endophilins-A, key endocytic proteins linked to neurodegeneration, directly regulate exocytosis by controlling vesicle recruitment, priming and fusion.Abstract FigureRecruitment, priming and fusion of secretory vesicles is controlled by endophilinLack of endophilins alters the distribution of secretory vesicles near the PMEndophilin’s role in exocytosis is mediated through its SH3-domainEndophilin regulates intersectin localization by keeping it away from the PM

scholarly journals Membrane curvature sensing of the lipid-anchored K-Ras small GTPase

2019 ◽  
Vol 2 (4) ◽  
pp. e201900343 ◽  
Author(s):  
Hong Liang ◽  
Huanwen Mu ◽  
Frantz Jean-Francois ◽  
Bindu Lakshman ◽  
Suparna Sarkar-Banerjee ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Cell Growth ◽  
Cell Shape ◽  
Membrane Curvature ◽  
Small Gtpase ◽  
Live Cells ◽  
Mitogenic Signaling ◽  
Curvature Sensing ◽  
Intracellular Organelle ◽  
Cell Property

Plasma membrane (PM) curvature defines cell shape and intracellular organelle morphologies and is a fundamental cell property. Growth/proliferation is more stimulated in flatter cells than the same cells in elongated shapes. PM-anchored K-Ras small GTPase regulates cell growth/proliferation and plays key roles in cancer. The lipid-anchored K-Ras form nanoclusters selectively enriched with specific phospholipids, such as phosphatidylserine (PS), for efficient effector recruitment and activation. K-Ras function may, thus, be sensitive to changing lipid distribution at membranes with different curvatures. Here, we used complementary methods to manipulate membrane curvature of intact/live cells, native PM blebs, and synthetic liposomes. We show that the spatiotemporal organization and signaling of an oncogenic mutant K-RasG12V favor flatter membranes with low curvature. Our findings are consistent with the more stimulated growth/proliferation in flatter cells. Depletion of endogenous PS abolishes K-RasG12V PM curvature sensing. In cells and synthetic bilayers, only mixed-chain PS species, but not other PS species tested, mediate K-RasG12V membrane curvature sensing. Thus, K-Ras nanoclusters act as relay stations to convert mechanical perturbations to mitogenic signaling.

Docking of chromaffin granules—A necessary step in exocytosis?

1987 ◽  
Vol 7 (4) ◽  
pp. 269-279 ◽  
Author(s):  
Theo Schäfer ◽  
Urs O. Karli ◽  
Felix E. Schweizer ◽  
Max M. Burger
Keyword(s):  
Plasma Membrane ◽  
Chromaffin Cells ◽  
Cell Types ◽  
Cell System ◽  
Secretory Vesicles ◽  
Chromaffin Granules ◽  
Permeabilized Cell ◽  
Permeabilized Cells ◽  
Pc 12 Cells

Putative docking of secretory vesicles comprising recognition of and attachment to future fusion sites in the plasma membrane has been investigated in chromaffin cells of the bovine adrenal medulla and in rat phaeochromocytoma (PC 12) cells. Upon permeabilization with digitonin, secretion can be stimulated in both cell types by indreasing the free Ca2+-concentration to μM levels. Secretory activity can be elicited up to 1 hr after starting permeabilization and despite the loss of soluble cytoplasmic components indicating a stable attachment of granules to the plasma membrane awaiting the trigger for fusion. Docked granules can be observed in the electron microscope in permeabilized PC 12 cells which contain a large proportion of their granules aligned underneath the plasma membrane. The population of putatively docked granules in chromaffin cells cannot be as readily discerned due to the dispersal of granules throughout the cytoplasm. Further experiments comparing PC 12 and chromaffin cells suggest that active docking but not transport of granules can still be performed by permeabilized cells in the presence of Ca2+: a short (2 min) pulse of Ca2+ in PC 12 cells leads to the secretion of almost all releasable hormone over a 15 min observation period whereas, in chromaffin cells, with only a small proportion of granules docked, withdrawal of Ca2+ leads to an immediate halt in secretion. Transport of chromaffin granules from the Golgi to the plasma membrane docking sites seems to depend on a mechanism sensitive to permeabilization. This is shown by the difference in the amount of hormone released from the two permeabilized cell types, reflecting the contrast in the proportion of granules docked to the plasma membrane in PC 12 or chromaffin cells. Neither docking nor the docked state are influenced by cytochalasine B or colchicine. The permeabilized cell system is a valuable technique for the in vitro study of interaction between secretory vesicles and their target membrane.

scholarly journals Phosphatidylinositol(4,5)bisphosphate coordinates actin-mediated mobilization and translocation of secretory vesicles to the plasma membrane of chromaffin cells

2011 ◽  
Vol 2 (1) ◽  
Author(s):  
Peter J. Wen ◽  
Shona L. Osborne ◽  
Mark Zanin ◽  
Pei Ching Low ◽  
Hai-Tao A. Wang ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Chromaffin Cells ◽  
Secretory Vesicles

scholarly journals C-terminal domain of mammalian complexin-1 localizes to highly curved membranes

2016 ◽  
Vol 113 (47) ◽  
pp. E7590-E7599 ◽  
Author(s):  
Jihong Gong ◽  
Ying Lai ◽  
Xiaohong Li ◽  
Mengxian Wang ◽  
Jeremy Leitz ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Neurotransmitter Release ◽  
Membrane Curvature ◽  
Neuronal Cultures ◽  
Spontaneous Release ◽  
Vesicle Membrane ◽  
Curvature Sensing ◽  
Postsynaptic Currents ◽  
Terminal Domain

In presynaptic nerve terminals, complexin regulates spontaneous “mini” neurotransmitter release and activates Ca2+-triggered synchronized neurotransmitter release. We studied the role of the C-terminal domain of mammalian complexin in these processes using single-particle optical imaging and electrophysiology. The C-terminal domain is important for regulating spontaneous release in neuronal cultures and suppressing Ca2+-independent fusion in vitro, but it is not essential for evoked release in neuronal cultures and in vitro. This domain interacts with membranes in a curvature-dependent fashion similar to a previous study with worm complexin [Snead D, Wragg RT, Dittman JS, Eliezer D (2014) Membrane curvature sensing by the C-terminal domain of complexin. Nat Commun 5:4955]. The curvature-sensing value of the C-terminal domain is comparable to that of α-synuclein. Upon replacement of the C-terminal domain with membrane-localizing elements, preferential localization to the synaptic vesicle membrane, but not to the plasma membrane, results in suppression of spontaneous release in neurons. Membrane localization had no measurable effect on evoked postsynaptic currents of AMPA-type glutamate receptors, but mislocalization to the plasma membrane increases both the variability and the mean of the synchronous decay time constant of NMDA-type glutamate receptor evoked postsynaptic currents.

scholarly journals Annexin A4 trimers are recruited by high membrane curvatures in Giant Plasma Membrane Vesicles

2020 ◽  
Author(s):  
Christoffer Florentsen ◽  
Alexander Kamp-Sonne ◽  
Guillermo Moreno-Pescador ◽  
Weria Pezeshkian ◽  
Ali Asghar Hakami Zanjani ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Membrane Vesicles ◽  
Membrane Curvature ◽  
Biological Functions ◽  
Membrane Repair ◽  
Plasma Membrane Vesicles ◽  
Curvature Sensing ◽  
Curved Structures ◽  
Annexin A4 ◽  
Membrane Budding

AbstractThe plasma membrane of eukaryotic cells consists of a crowded environment comprised of a high diversity of proteins in a complex lipid matrix. The lateral organization of membrane proteins in the plasma membrane (PM) is closely correlated with biological functions such as endocytosis, membrane budding and other processes which involve protein mediated shaping of the membrane into highly curved structures. Annexin A4 (ANXA4) is a prominent player in a number of biological functions including plasma membrane repair. Its binding to membranes is activated by Ca2+ influx and it is therefore rapidly recruited to the cell surface near rupture sites where Ca2+ influx takes place. However, the free edges near rupture sites can easily bend into complex curvatures and hence may accelerate recruitment of curvature sensing proteins to facilitate rapid membrane repair. To analyze the curvature sensing behavior of curvature inducing proteins in crowded membranes, we quantifify the affinity of ANXA4 monomers and trimers for high membrane curvatures by extracting membrane nanotubes from giant plasma membrane vesicles (GPMVs). ANXA4 is found to be a sensor of negative membrane curvatures. Multiscale simulations furthermore predicted that ANXA4 trimers generate membrane curvature upon binding and have an affinity for highly curved membrane regions only within a well defined membrane curvature window. Our results indicate that curvature sensing and mobility of ANXA4 depend on the trimer structure of ANXA4 which could provide new biophysical insight into the role of ANXA4 in membrane repair and other biological processes.

scholarly journals Evidence for Functional Localization of the Proenkephalin-Processing Enzyme, Prohormone Thiol Protease, to Secretory Vesicles of Chromaffin Cells*

Endocrinology ◽  
1999 ◽  
Vol 140 (8) ◽  
pp. 3744-3754 ◽  
Author(s):  
Vivian Y. H. Hook ◽  
Stephen Noctor ◽  
Catherine A. Sei ◽  
Thomas Toneff ◽  
Sukkid Yasothornsrikul ◽  
...  
Keyword(s):  
Chromaffin Cells ◽  
Secretory Vesicles ◽  
Thiol Protease ◽  
Processing Enzyme ◽  
Functional Localization

scholarly journals Membrane curvature sensing by the C-terminal domain of complexin

2014 ◽  
Vol 5 (1) ◽  
Author(s):  
David Snead ◽  
Rachel T. Wragg ◽  
Jeremy S. Dittman ◽  
David Eliezer
Keyword(s):  
Membrane Curvature ◽  
Curvature Sensing ◽  
Terminal Domain
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