Association of SNAREs and Calcium Channels with the Borders of Cytoskeletal Cages Organizes the Secretory Machinery in Chromaffin Cells

Torregrosa‐Hetland, Cristina J.; Villanueva, José; López-Font, Inmaculada; García-Martínez, Virginia; Gil, Amparo; González‐Vélez, Virginia; Segura, Javier; Viniegra, Salvador; Gutiérrez, Luis M.

doi:10.1007/s10571-010-9565-1

Cited by 17 publications

(13 citation statements)

References 37 publications

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“…Recent studies performed on neuroendocrine chromaffin cells reported the association of SNARE protein patches and clusters of voltage-gated Ca 2ϩ channels with the borders of cortical cytoskeletal cages (68,69). We show here the glucoseresponsive colocalization of Ca 2ϩ -responsive FAK (27) with ␤1 integrin and paxillin in patches at the basal ␤ cell membrane.…”

Section: Discussionsupporting

confidence: 54%

Novel Mechanistic Link between Focal Adhesion Remodeling and Glucose-stimulated Insulin Secretion

Rondas

Tomás

Soto-Ribeiro

et al. 2012

Journal of Biological Chemistry

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Actin cytoskeleton remodeling is well known to be positively involved in glucose-stimulated pancreatic β cell insulin secretion. We have observed glucose-stimulated focal adhesion remodeling at the β cell surface and have shown this to be crucial for glucose-stimulated insulin secretion. However, the mechanistic link between such remodeling and the insulin secretory machinery remained unknown and was the major aim of this study. MIN6B1 cells, a previously validated model of primary β cell function, were used for all experiments. Total internal reflection fluorescence microscopy revealed the glucose-responsive co-localization of focal adhesion kinase (FAK) and paxillin with integrin β1 at the basal cell surface after short term stimulation. In addition, blockade of the interaction between β1 integrins and the extracellular matrix with an anti-β1 integrin antibody (Ha2/5) inhibited short term glucose-induced phosphorylation of FAK (Tyr-397), paxillin (Tyr-118), and ERK1/2 (Thr-202/Tyr-204). Pharmacological inhibition of FAK activity blocked glucose-induced actin cytoskeleton remodeling and glucose-induced disruption of the F-actin/SNAP-25 association at the plasma membrane as well as the distribution of insulin granules to regions in close proximity to the plasma membrane. Furthermore, FAK inhibition also completely blocked short term glucose-induced activation of the Akt/AS160 signaling pathway. In conclusion, these results indicate 1) that glucose-induced activation of FAK, paxillin, and ERK1/2 is mediated by β1 integrin intracellular signaling, 2) a mechanism whereby FAK mediates glucose-induced actin cytoskeleton remodeling, hence allowing docking and fusion of insulin granules to the plasma membrane, and 3) a possible functional role for the Akt/AS160 signaling pathway in the FAK-mediated regulation of glucose-stimulated insulin secretion.

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Section: Discussionsupporting

confidence: 54%

Novel Mechanistic Link between Focal Adhesion Remodeling and Glucose-stimulated Insulin Secretion

Rondas

Tomás

Soto-Ribeiro

et al. 2012

Journal of Biological Chemistry

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“…Indeed the majority of SGs in the vicinity of the plasma membrane are tethered to the cortical actin network (6), and newly arriving vesicles are also caught in this dense mesh of F-actin (33). Other studies point to the existence of F-actin cages that organize the SNARE proteins SNAP25 and syntaxin-1 as well as L- and P/Q-type calcium channels, creating sites in the cortical actin network where SGs fuse preferentially (34). Consistent with these data, studies using total internal reflection fluorescence (TIRF) microscopy revealed that vesicle motion becomes restricted in the vicinity of the plasma membrane (35, 36).…”

Section: New Roles For Actin In Exocytosismentioning

confidence: 99%

The Cortical Acto-Myosin Network: From Diffusion Barrier to Functional Gateway in the Transport of Neurosecretory Vesicles to the Plasma Membrane

et al. 2013

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Dysregulation of regulated exocytosis is linked to an array of pathological conditions, including neurodegenerative disorders, asthma, and diabetes. Understanding the molecular mechanisms underpinning neuroexocytosis including the processes that allow neurosecretory vesicles to access and fuse with the plasma membrane and to recycle post-fusion, is therefore critical to the design of future therapeutic drugs that will efficiently tackle these diseases. Despite considerable efforts to determine the principles of vesicular fusion, the mechanisms controlling the approach of vesicles to the plasma membrane in order to undergo tethering, docking, priming, and fusion remain poorly understood. All these steps involve the cortical actin network, a dense mesh of actin filaments localized beneath the plasma membrane. Recent work overturned the long-held belief that the cortical actin network only plays a passive constraining role in neuroexocytosis functioning as a physical barrier that partly breaks down upon entry of Ca2+ to allow secretory vesicles to reach the plasma membrane. A multitude of new roles for the cortical actin network in regulated exocytosis have now emerged and point to highly dynamic novel functions of key myosin molecular motors. Myosins are not only believed to help bring about dynamic changes in the actin cytoskeleton, tethering and guiding vesicles to their fusion sites, but they also regulate the size and duration of the fusion pore, thereby directly contributing to the release of neurotransmitters and hormones. Here we discuss the functions of the cortical actin network, myosins, and their effectors in controlling the processes that lead to tethering, directed transport, docking, and fusion of exocytotic vesicles in regulated exocytosis.

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“…Thus, the study of the secretory organization in neurite-alike structures in chromaffin cells appeared interesting to understand the fine-tuning of exocytosis when the endocrine organization evolves to a pseudoneuronal system. In addition to studying such organization, we use stochastic models of secretion (Gil et al 2000;Torregrosa-Hetland et al 2010Villanueva et al 2010) to study the influence of calcium channel accumulation and cytoskeletal organization in determining the kinetic differences in secretion found between neurite terminals and the cell body. Our study enriches the variety of roles assumed by the cortical cytoskeleton when governing the secretory process (Gutierrez 2012).…”

Section: Introductionmentioning

confidence: 99%

Neurite extensions in chromaffin cells: study of the influence of the cytoskeletal structure on calcium dynamics and secretion

Gil

Torregrosa‐Hetland

González‐Vélez

et al. 2012

Frontiers in Life Science

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The extension of neurites by bovine chromaffin cells in culture represents an opportunity to analyse the factors contributing to shape secretion from a round endocrine to a polarized neuronal model. Neurite-emitting chromaffin cells indeed present a different cytoskeletal organization characterized by smaller cytoskeletal cages when compared to round cells and also show a higher density of P/Q-type calcium channels at the neurite tips. Furthermore, these cells present faster and more transient secretory kinetics at the neurite processes when compared with the secretory activity found in round cells. These results were taken into account when proposing a stochastic mathematical model to analyse the impact of different factors in intracellular calcium elevations and the resulting secretory kinetics. Thus, our modelling studies predict that the accumulation of calcium channels at the neurite tips is a major cause of accelerated secretory kinetics, whereas reducing the space for calcium diffusion consequence of smaller cytoskeletal cages enhances the sensitivity of secretion to lower calcium concentrations when assuming a porosity factor for calcium crossing F-actin structures.

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Association of SNAREs and Calcium Channels with the Borders of Cytoskeletal Cages Organizes the Secretory Machinery in Chromaffin Cells

Cited by 17 publications

References 37 publications

Novel Mechanistic Link between Focal Adhesion Remodeling and Glucose-stimulated Insulin Secretion

Novel Mechanistic Link between Focal Adhesion Remodeling and Glucose-stimulated Insulin Secretion

The Cortical Acto-Myosin Network: From Diffusion Barrier to Functional Gateway in the Transport of Neurosecretory Vesicles to the Plasma Membrane

Neurite extensions in chromaffin cells: study of the influence of the cytoskeletal structure on calcium dynamics and secretion

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