'Should I stay or should I go?': myosin V function in organelle trafficking.
Journal - Biology of the cell / under the auspices of the European Cell Biology Organization (England )
Actin- and microtubule-based motors can propel different cargos along filaments. Within cells, they control the distribution of membrane-bound compartments by performing complementary tasks. Organelles make long journeys along microtubules, with class V myosins ensuring their capture and their dispersal in actin-rich regions. Myosin Va is recruited on to diverse organelles, such as melanosomes and secretory vesicles, by a mechanism involving Rab GTPases. The role of myosin Va in the recruitment of secretory vesicles at the plasma membrane reveals that the cortical actin network cannot merely be seen as a physical barrier hindering vesicle access to release sites. In neurons, myosin Va controls the targeting of IP(3) (inositol 1,4,5-trisphosphate)-sensitive Ca(2+) stores to dendritic spines and the transport of mRNAs. These defects probably account for the severe neurological symptoms observed in Griscelli syndrome due to mutations in the MYO5A gene.
|ISSN : ||1768-322X|
|Mesh Heading : ||Animals Biological Transport Humans Melanosomes Myosin Type V Organelles Secretory Vesicles metabolism metabolism|
|Mesh Heading Relevant : ||metabolism metabolism|
Myosin va mediates docking of secretory granules at the plasma membrane.
Journal - The Journal of neuroscience : the official journal of the Society for Neuroscience (United States )
Myosin Va (MyoVa) is a prime candidate for controlling actin-based organelle motion in neurons and neuroendocrine cells. Its function in secretory granule (SG) trafficking was investigated in enterochromaffin cells by wide-field and total internal reflection fluorescence microscopy. The distribution of endogenous MyoVa partially overlapped with SGs and microtubules. Impairing MyoVa function by means of a truncated construct (MyoVa tail) or RNA interference prevented the formation of SG-rich regions at the cell periphery and reduced SG density in the subplasmalemmal region. Individual SG trajectories were tracked to analyze SG mobility. A wide distribution of their diffusion coefficient, D(xy), was observed. Almost immobile SGs (D(xy) < 5 x 10(-4) microm2 x s(-1)) were considered as docked at the plasma membrane based on two properties: (1) SGs that undergo exocytosis have a D(xy) below this threshold value for at least 2 s before fusion; (2) a negative autocorrelation of the vertical motion was found in subtrajectories with a D(xy) below the threshold. Using this criterion of docking, we found that the main effect of MyoVa inhibition was to reduce the number of docked granules, leading to reduced secretory responses. Surprisingly, this reduction was not attributable to a decreased transport of SGs toward release sites. In contrast, MyoVa silencing reduced the occurrence of long-lasting, but not short-lasting, docking periods. We thus propose that, despite its known motor activity, MyoVa directly mediates stable attachment of SGs at the plasma membrane.
|ISSN : ||1529-2401|
|Mesh Heading : ||Cell Membrane Cells, Cultured Humans Myosin Heavy Chains Myosin Type V Secretory Vesicles Transport Vesicles physiology|
|Mesh Heading Relevant : ||physiology physiology physiology physiology|
Rab27A and its effector MyRIP link secretory granules to F-actin and control their motion towards release sites.
Journal - The Journal of cell biology (United States )
The GTPase Rab27A interacts with myosin-VIIa and myosin-Va via MyRIP or melanophilin and mediates melanosome binding to actin. Here we show that Rab27A and MyRIP are associated with secretory granules (SGs) in adrenal chromaffin cells and PC12 cells. Overexpression of Rab27A, GTPase-deficient Rab27A-Q78L, or MyRIP reduced secretory responses of PC12 cells. Amperometric recordings of single adrenal chromaffin cells revealed that Rab27A-Q78L and MyRIP reduced the sustained component of release. Moreover, these effects on secretion were partly suppressed by the actin-depolymerizing drug latrunculin but strengthened by jasplakinolide, which stabilizes the actin cortex. Finally, MyRIP and Rab27A-Q78L restricted the motion of SGs in the subplasmalemmal region of PC12 cells, as measured by evanescent-wave fluorescence microscopy. In contrast, the Rab27A-binding domain of MyRIP and a MyRIP construct that interacts with myosin-Va but not with actin increased the mobility of SGs. We propose that Rab27A and MyRIP link SGs to F-actin and control their motion toward release sites through the actin cortex.
|ISSN : ||0021-9525|
|Mesh Heading : ||Actins Adaptor Proteins, Signal Transducing Animals Bicyclo Compounds, Heterocyclic Carrier Proteins Cattle Chromaffin Cells Exocytosis Microfilaments Microscopy, Electron Myosin Heavy Chains Myosin Type V PC12 Cells Peptides, Cyclic Rats Secretory Vesicles Thiazoles Thiazolidines rab GTP-Binding Proteins antagonists & inhibitors pharmacology genetics metabolism ultrastructure drug effects genetics drug effects metabolism ultrastructure metabolism metabolism pharmacology metabolism ultrastructure pharmacology genetics|
|Mesh Heading Relevant : ||Depsipeptides metabolism metabolism secretion secretion metabolism|
Long term stimulation changes the vesicular monoamine transporter content of chromaffin granules.
Journal - The Journal of biological chemistry (UNITED STATES )
Bovine chromaffin cells cultured for 5 days in the presence of depolarizing concentrations of K+ ions show a decreased number of secretory (chromaffin) granules per cell. These cells were still capable of exocytosis. Their contents in catecholamine and chromogranin A, components of the granule matrix, and cytochrome b561, a major protein of the granule membrane, were decreased to 35, 30, and 50% of control cells, respectively. However, in the same cells, the number of [3H]dihydrotetrabenazine binding sites, a specific ligand of the vesicular monoamine transporter, was increased to 180% of controls. In situ uptake of noradrenaline in permeabilized cells indicated that [3H]dihydrotetrabenazine binding sites were associated with a functional vesicular monoamine transporter. When analyzed by isopycnic centrifugation, these sites cosedimented with catecholamine, chromogranin A, and cytochrome b561, in a peak with a density lighter than that from controls. The composition of this peak suggests that it contains incompletely matured secretory granules, with a 3-5-fold increase in the vesicular monoamine transporter content of this membrane. This increase might indicate that an adaptative process occurs which allows a faster filling of the granules in continuously secreting cells.
|ISSN : ||0021-9258|
|Mesh Heading : ||Animals Biological Transport Catecholamines Cattle Cell Fractionation Cell Membrane Permeability Cells, Cultured Chromaffin Granules Chromaffin System Chromogranin A Chromogranins Cytochrome b Group Exocytosis Fluorescent Antibody Technique Glycoproteins Intracellular Membranes Norepinephrine Potassium Stimulation, Chemical Tetrabenazine Tyrosine 3-Monooxygenase Vesicular Biogenic Amine Transport Proteins Vesicular Monoamine Transport Proteins metabolism cytology ultrastructure isolation & purification analysis metabolism pharmacology analogs & derivatives metabolism isolation & purification|
|Mesh Heading Relevant : ||Membrane Glycoproteins Membrane Transport Proteins Neuropeptides metabolism metabolism metabolism|
Rab27A and its effector MyRIP link secretory granules to F-actin and control their motion towards release sites
Journal - The Journal of Cell Biology
The GTPase Rab27A interacts with myosin-VIIa and myosin-Va viaMyRIP or melanophilin and mediates melanosome binding to actin.Here we show that Rab27A and MyRIP are associated with secretorygranules (SGs) in adrenal chromaffin cells and PC12 cells. Overexpressionof Rab27A, GTPase-deficient Rab27A-Q78L, or MyRIP reduced secretoryresponses of PC12 cells. Amperometric recordings of single adrenalchromaffin cells revealed that Rab27A-Q78L and MyRIP reducedthe sustained component of release. Moreover, these effectson secretion were partly suppressed by the actin-depolymerizingdrug latrunculin but strengthened by jasplakinolide, which stabilizesthe actin cortex. Finally, MyRIP and Rab27A-Q78L restrictedthe motion of SGs in the subplasmalemmal region of PC12 cells,as measured by evanescent-wave fluorescence microscopy. In contrast,the Rab27A-binding domain of MyRIP and a MyRIP construct thatinteracts with myosin-Va but not with actin increased the mobilityof SGs. We propose that Rab27A and MyRIP link SGs to F-actinand control their motion toward release sites through the actincortex.
The online version of this article includes supplemental material.
Abbreviations used in this paper: 5-HT, 5-hydroxytryptamine;CTL, cytotoxic T lymphocyte; EW-FM, evanescent wave fluorescencemicroscopy; hGH, human growth hormone; MSD, mean square displacement;NPY, neuropeptide Y; SERT, serotonin transporter; SG, secretorygranule.
|Keywords : ||Rab27A; MyRIP; exocytosis; actin; neuroendocrine cell|