scholarly journals Cortical F-Actin, the Exocytic Mode, and Neuropeptide Release in Mouse Chromaffin Cells Is Regulated by Myristoylated Alanine-rich C-Kinase Substrate and Myosin II

2009 ◽  
Vol 20 (13) ◽  
pp. 3142-3154 ◽  
Author(s):  
Bryan W. Doreian ◽  
Tiberiu G. Fulop ◽  
Robert L. Meklemburg ◽  
Corey B. Smith
Keyword(s):  
Chromaffin Cells ◽  
Myosin Ii ◽  
Splanchnic Nerve ◽  
Cortical Actin ◽  
Kinase Substrate ◽  
Actin Cortex ◽  
Collapse Mode ◽  
Associated Proteins ◽  
Intact Cortex ◽  
Activity Dependent

Adrenal medullary chromaffin cells are innervated by the sympathetic splanchnic nerve and translate graded sympathetic firing into a differential hormonal exocytosis. Basal sympathetic firing elicits a transient kiss-and-run mode of exocytosis and modest catecholamine release, whereas elevated firing under the sympathetic stress response results in full granule collapse to release catecholamine and peptide transmitters into the circulation. Previous studies have shown that rearrangement of the cell actin cortex regulates the mode of exocytosis. An intact cortex favors kiss-and-run exocytosis, whereas disrupting the cortex favors the full granule collapse mode. Here, we investigate the specific roles of two actin-associated proteins, myosin II and myristoylated alanine-rich C-kinase substrate (MARCKS) in this process. Our data demonstrate that MARCKS phosphorylation under elevated cell firing is required for cortical actin disruption but is not sufficient to elicit peptide transmitter exocytosis. Our data also demonstrate that myosin II is phospho-activated under high stimulation conditions. Inhibiting myosin II activity prevented disruption of the actin cortex, full granule collapse, and peptide transmitter release. These results suggest that phosphorylation of both MARCKS and myosin II lead to disruption of the actin cortex. However, myosin II, but not MARCKS, is required for the activity-dependent exocytosis of the peptide transmitters.

scholarly journals Generation of stress fibers through myosin-driven re-organization of the actin cortex

2020 ◽  
Author(s):  
JI Lehtimäki ◽  
EK Rajakylä ◽  
S Tojkander ◽  
P Lappalainen
Keyword(s):  
De Novo ◽  
Myosin Ii ◽  
Focal Adhesions ◽  
Stress Fibers ◽  
Cell Cortex ◽  
Cortical Actin ◽  
Cellular Processes ◽  
Actin Cortex ◽  
Muscle Myosin ◽  
Subsequent Stabilization

SummaryContractile actomyosin bundles, stress fibers, govern key cellular processes including migration, adhesion, and mechanosensing. Stress fibers are thus critical for developmental morphogenesis. The most prominent actomyosin bundles, ventral stress fibers, are generated through coalescence of pre-existing stress fiber precursors. However, whether stress fibers can assemble through other mechanisms has remained elusive. We report that stress fibers can also form without requirement of pre-existing actomyosin bundles. These structures, which we named cortical stress fibers, are embedded in the cell cortex and assemble preferentially underneath the nucleus. In this process, non-muscle myosin II pulses orchestrate the reorganization of cortical actin meshwork into regular bundles, which promote reinforcement of nascent focal adhesions, and subsequent stabilization of the cortical stress fibers. These results identify a new mechanism by which stress fibers can be generated de novo from the actin cortex, and establish role for stochastic myosin pulses in the assembly of functional actomyosin bundles.

scholarly journals Generation of stress fibers through myosin-driven reorganization of the actin cortex

eLife ◽  
2021 ◽  
Vol 10 ◽  
Author(s):  
Jaakko I Lehtimäki ◽  
Eeva Kaisa Rajakylä ◽  
Sari Tojkander ◽  
Pekka Lappalainen
Keyword(s):  
De Novo ◽  
Myosin Ii ◽  
Focal Adhesions ◽  
Stress Fibers ◽  
Cell Cortex ◽  
Cortical Actin ◽  
Cellular Processes ◽  
Actin Cortex ◽  
Muscle Myosin ◽  
Subsequent Stabilization

Contractile actomyosin bundles, stress fibers, govern key cellular processes including migration, adhesion, and mechanosensing. Stress fibers are thus critical for developmental morphogenesis. The most prominent actomyosin bundles, ventral stress fibers, are generated through coalescence of pre-existing stress fiber precursors. However, whether stress fibers can assemble through other mechanisms has remained elusive. We report that stress fibers can also form without requirement of pre-existing actomyosin bundles. These structures, which we named cortical stress fibers, are embedded in the cell cortex and assemble preferentially underneath the nucleus. In this process, non-muscle myosin II pulses orchestrate the reorganization of cortical actin meshwork into regular bundles, which promote reinforcement of nascent focal adhesions, and subsequent stabilization of the cortical stress fibers. These results identify a new mechanism by which stress fibers can be generated de novo from the actin cortex and establish role for stochastic myosin pulses in the assembly of functional actomyosin bundles.

scholarly journals Nongenomic Glucocorticoid Effects on Activity-Dependent Potentiation of Catecholamine Release in Chromaffin Cells

Endocrinology ◽  
2008 ◽  
Vol 149 (10) ◽  
pp. 4921-4927 ◽  
Author(s):  
Yong-Soo Park ◽  
Yoon Ha Choi ◽  
Choon-Ho Park ◽  
Kyong-Tai Kim
Keyword(s):  
Chromaffin Cells ◽  
Glucocorticoid Receptors ◽  
Inhibitory Effect ◽  
Term Treatment ◽  
Catecholamine Release ◽  
Dependent Manner ◽  
Short Term ◽  
Short Term Treatment ◽  
Kinase Substrate ◽  
Activity Dependent

Adrenal medulla chromaffin cells are neuroendocrine and modified sympathetic ganglion cells. Catecholamines released from chromaffin cells mediate the fight-or-flight response or alert reaction against dangerous conditions. Here we report that short-term treatment with glucocorticoids, released from adrenal cortex cells in response to chronic stress, inhibits activity-dependent potentiation (ADP) of catecholamine release. First, short-term treatment with dexamethasone (DEX), a synthetic glucocorticoid, reduces ADP in a concentration-dependent manner (IC50 324.2 ± 54.5 nm). The inhibitory effect of DEX is not reversed by RU-486 treatment, suggesting that the rapid inhibitory effect of DEX on ADP of catecholamine release is independent of glucocorticoid receptors. Second, DEX treatment reduces the frequency of fusion between vesicles and plasma membrane without affecting calcium influx. DEX disrupts activity-induced vesicle translocation and F-actin disassembly, thereby leading to inhibition of the vesicle fusion frequency. Third, we provide evidence that DEX reduces F-actin disassembly via inhibiting phosphorylation and translocation of myristoylated alanine-rich C kinase substrate and its upstream kinase protein kinase Cε. Altogether, we suggest that glucocorticoids inhibit ADP of catecholamine release by decreasing myristoylated alanine-rich C kinase substrate phosphorylation, which inhibits F-actin disassembly and vesicle translocation.

scholarly journals Specific release of membrane-bound annexin II and cortical cytoskeletal elements by sequestration of membrane cholesterol.

1997 ◽  
Vol 8 (3) ◽  
pp. 533-545 ◽  
Author(s):  
T Harder ◽  
R Kellner ◽  
R G Parton ◽  
J Gruenberg
Keyword(s):  
Actin Cytoskeleton ◽  
Cytoskeletal Proteins ◽  
Annexin Ii ◽  
Dependent Manner ◽  
Cortical Actin ◽  
Independent Manner ◽  
Low Concentrations ◽  
Early Endosomes ◽  
Associated Proteins ◽  
Cytoskeletal Elements

Annexin II is an abundant protein which is present in the cytosol and on the cytoplasmic face of plasma membrane and early endosomes. It is generally believed that this association occurs via Ca(2+)-dependent binding to lipids, a mechanism typical for the annexin protein family. Although previous studies have shown that annexin II is involved in early endosome dynamics and organization, the precise biological role of the protein is unknown. In this study, we found that approximately 50% of the total cellular annexin was associated with membranes in a Ca(2+)-independent manner. This binding was extremely tight, since it resisted high salt and, to some extent, high pH treatments. We found, however, that membrane-associated annexin II could be quantitatively released by low concentrations of the cholesterol-sequestering agents filipin and digitonin. Both treatments released an identical and limited set of proteins but had no effects on other membrane-associated proteins. Among the released proteins, we identified, in addition to annexin II itself, the cortical cytoskeletal proteins alpha-actinin, ezrin and moesin, and membrane-associated actin. Our biochemical and immunological observations indicate that these proteins are part of a complex containing annexin II and that stability of the complex is sensitive to cholesterol sequestering agents. Since annexin II is tightly membrane-associated in a cholesterol-dependent manner, and since it seems to interact physically with elements of the cortical actin cytoskeleton, we propose that the protein serves as interface between membranes containing high amounts of cholesterol and the actin cytoskeleton.

scholarly journals The Annexin A2/S100A10 System in Health and Disease: Emerging Paradigms

2012 ◽  
Vol 2012 ◽  
pp. 1-13 ◽  
Author(s):  
Nadia Hedhli ◽  
Domenick J. Falcone ◽  
Bihui Huang ◽  
Gabriela Cesarman-Maus ◽  
Rosemary Kraemer ◽  
...  
Keyword(s):  
Serotonin Receptor ◽  
Human Cancer ◽  
High Titer ◽  
Critical Role ◽  
Annexin A2 ◽  
Avascular Osteonecrosis ◽  
Kinase Substrate ◽  
New Findings ◽  
Human Disorders ◽  
Associated Proteins

Since its discovery as a src kinase substrate more than three decades ago, appreciation for the physiologic functions of annexin A2 and its associated proteins has increased dramatically. With its binding partner S100A10 (p11), A2 forms a cell surface complex that regulates generation of the primary fibrinolytic protease, plasmin, and is dynamically regulated in settings of hemostasis and thrombosis. In addition, the complex is transcriptionally upregulated in hypoxia and promotes pathologic neoangiogenesis in the tissues such as the retina. Dysregulation of both A2 and p11 has been reported in examples of rodent and human cancer. Intracellularly, A2 plays a critical role in endosomal repair in postarthroplastic osteolysis, and intracellular p11 regulates serotonin receptor activity in psychiatric mood disorders. In human studies, the A2 system contributes to the coagulopathy of acute promyelocytic leukemia, and is a target of high-titer autoantibodies in patients with antiphospholipid syndrome, cerebral thrombosis, and possibly preeclampsia. Polymorphisms in the humanANXA2gene have been associated with stroke and avascular osteonecrosis of bone, two severe complications of sickle cell disease. Together, these new findings suggest that manipulation of the annexin A2/S100A10 system may offer promising new avenues for treatment of a spectrum of human disorders.

scholarly journals Myosin-II activity generates a dynamic steady state with continuous actin turnover in a minimal actin cortex

2018 ◽  
Author(s):  
Sonal ◽  
Kristina A. Ganzinger ◽  
Sven K. Vogel ◽  
Jonas Mücksch ◽  
Philipp Blumhardt ◽  
...  
Keyword(s):  
Steady State ◽  
Actin Polymerization ◽  
Myosin Ii ◽  
Fine Tuning ◽  
Cellular Functions ◽  
Actin Cortex ◽  
Actin Turnover ◽  
Cytoskeletal Dynamics

ABSTRACTDynamic reorganization of the actomyosin cytoskeleton allows a fine-tuning of cell shape that is vital to many cellular functions. It is well established that myosin-II motors generate the forces required for remodeling the cell surface by imparting contractility to actin networks. An additional, less understood, role of myosin-II in cytoskeletal dynamics is believed to be in the regulation of actin turnover; it has been proposed that myosin activity increases actin turnover in various cellular contexts, presumably by contributing to disassembly. In vitro reconstitution of actomyosin networks has confirmed the role of myosin in actin network disassembly, but factors such as diffusional constraints and the use of stabilized filaments have thus far limited the observation of myosin-assisted actin turnover in these networks. Here, we present the reconstitution of a minimal dynamic actin cortex where actin polymerization is catalyzed on the membrane in the presence of myosin-II activity. We demonstrate that myosin activity leads to disassembly and redistribution in this simplified cortex. Consequently, a new dynamic steady state emerges in which actin filaments undergo constant turnover. Our findings suggest a multi-faceted role of myosin-II in fast remodeling of the eukaryotic actin cortex.

scholarly journals Dia- and Rok-dependent enrichment of capping proteins in a cortical region

2021 ◽  
Author(s):  
Anja Schmidt ◽  
Long Li ◽  
Zhiyi Lv ◽  
Shuling Yan ◽  
Jörg Großhans
Keyword(s):  
Myosin Ii ◽  
Rho Kinase ◽  
Cortical Region ◽  
Protein Enrichment ◽  
Cortical Actin ◽  
Capping Protein ◽  
Capping Proteins ◽  
Muscle Myosin ◽  
Drosophila Embryos

Rho signaling with its major targets the formin Dia, Rho kinase (Rok) and non-muscle myosin II control turnover, amount and contractility of actomyosin. Much less investigated has been a potential function for the distribution of F-actin plus and minus ends. In syncytial Drosophila embryos Rho1 signaling is high between actin caps, i. e. the cortical intercap region. Capping protein binds to free plus ends of F-actin to prevent elongation of the filament. Capping protein has served as a marker to visualize the distribution of F-actin plus ends in cells and in vitro. Here, we probed the distribution of plus ends with capping protein in syncytial Drosophila embryos. We found that Capping proteins are specifically enriched in the intercap region similar to Dia and MyoII but distinct from overall F-actin. The intercap enrichment of Capping protein was impaired in dia mutants and embryos, in which Rok and MyoII activation was inhibited. Our observations reveal that Dia and Rok/MyoII control Capping protein enrichment and support a model that Dia and Rok/MyoII control the organization of cortical actin cytoskeleton downstream of Rho1 signaling.

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