Regulation of insulin exocytosis by calcium-dependent protein kinase C in beta cells

Trexler, Adam J.; Taraska, Justin W.

doi:10.1016/j.ceca.2017.07.008

Cited by 38 publications

(25 citation statements)

References 163 publications

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“…Exocytosis is dependent on the formation of the soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) complex. This complex is composed of three main components: the vesicle-bound VAMP2, which binds to two target membrane proteins, syntaxin1A and SNAP25 (45). It was shown that SNAP25 in neuronal cells can directly interact with the conventional Gβγ complexes, influencing neurotransmitter release (46)(47)(48).…”

Section: Discussionmentioning

confidence: 99%

The regulatory G protein signaling complex, Gβ5–R7, promotes glucose- and extracellular signal–stimulated insulin secretion

Wang

Henry

Pronin

et al. 2020

Journal of Biological Chemistry

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G protein–coupled receptors (GPCRs) are important modulators of glucose-stimulated insulin secretion, essential for maintaining energy homeostasis. Here we investigated the role of Gβ5–R7, a protein complex consisting of the atypical G protein β subunit Gβ5 and a regulator of G protein signaling of the R7 family. Using the mouse insulinoma MIN6 cell line and pancreatic islets, we investigated the effects of G protein subunit β 5 (Gnb5) knockout on insulin secretion. Consistent with previous work, Gnb5 knockout diminished insulin secretion evoked by the muscarinic cholinergic agonist Oxo-M. We found that the Gnb5 knockout also attenuated the activity of other GPCR agonists, including ADP, arginine vasopressin, glucagon-like peptide 1, and forskolin, and, surprisingly, the response to high glucose. Experiments with MIN6 cells cultured at different densities provided evidence that Gnb5 knockout eliminated the stimulatory effect of cell adhesion on Oxo-M–stimulated glucose–stimulated insulin secretion; this effect likely involved the adhesion GPCR GPR56. Gnb5 knockout did not influence cortical actin depolymerization but affected protein kinase C activity and the 14-3-3ϵ substrate. Importantly, Gnb5−/− islets or MIN6 cells had normal total insulin content and released normal insulin amounts in response to K+-evoked membrane depolarization. These results indicate that Gβ5–R7 plays a role in the insulin secretory pathway downstream of signaling via all GPCRs and glucose. We propose that the Gβ5–R7 complex regulates a phosphorylation event participating in the vesicular trafficking pathway downstream of G protein signaling and actin depolymerization but upstream of insulin granule release.

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Section: Discussionmentioning

confidence: 99%

The regulatory G protein signaling complex, Gβ5–R7, promotes glucose- and extracellular signal–stimulated insulin secretion

Wang

Henry

Pronin

et al. 2020

Journal of Biological Chemistry

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“…Pancreatic β-cells express several isoforms of PKC, which are thought to play different roles in GSIS (Trexler and Taraska, 2017). They are activated during high glucose conditions and influence insulin exocytosis by activating components of the exocytotic machinery.…”

Section: Pkc Is Responsible For Endosomal Degradation and Downregulamentioning

confidence: 99%

“…The second phase is associated with an increased production of DAG (Wolf et al, 1990) and activation of several PKC isoforms (,β, and ) in the β-cell (Trexler and Taraska, 2017;Warwar et al, 2006). The different PKC isoforms appear to target different components of machinery associated with insulin secretion (Trexler and Taraska, 2017). In relation to the KATP channel, an yet-to-be identified PKC isoform activates the channel via threonine180 phosphorylation at Kir6.2 (Light et al, 2000).…”

Section: Possible Patho-physiological Significance Of the Current Finmentioning

confidence: 99%

Protein kinase Cε activation induces EHD-dependent degradation and downregulation of K_ATPchannels: Implications for glucose stimulated insulin secretion

Cockcroft

Manna

Karnik

et al. 2020

Preprint

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Pancreatic β-cells have the unique ability to couple glucose metabolism to insulin secretion. This capacity is generally attributed to the ability of ATP to inhibit KATP channels, and the consequent β-cell membrane depolarization and excitation. This notion has recently been challenged by a study which demonstrated that high glucose (HG) downregulates the cell surface KATP channels, and thereby leads to β-cell depolarisation and excitation. The authors attributed the downregulation to HG-induced protein kinase C (PKC) activation and the consequent increase in channel endocytosis. This interpretation, however, is inconsistent with our previous findings that PKC activation does not affect endocytosis. To address this controversy, we revisited the problem: we have used cell biological and electrophysiological approaches combined with the pharmacological activator of PKC, PMA (phorbol 12-myristate 13-acetate). We first confirm that PKC does not play a role in KATP channel endocytosis; instead, it downregulates the channel by promoting lysosomal degradation coupled with reduced recycling. We then show that (i) mutation of the dileucine motif ( 355 LL 356 ) in the Cterminal domain of the Kir6.2 subunit of the KATP channel complex prevents lysosomal degradation; (ii) lysosomal targeting is mediated by the EHD (Eps15 homology domaincontaining) proteins; and (iii) the PKC isoform responsible for channel degradation is PKC.Taken together with the published data, we suggest that HG promotes β-cell excitability via two mechanisms: ATP-dependent channel inhibition and ATP-independent, PKC-dependent channel degradation. The results likely have implications for glucose induced biphasic insulin secretion.

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“…We began by examining the temporal dynamics of regulatory lipids at individual sites of exocytosis of MMP-9 in MCF-7 cells. In regulated exocytosis, the importance of regulatory lipids, PIP2 and DAG, are well documented as secondary messengers involved in several cellular signaling pathways [50], including the distinct steps of regulated exocytosis [28,31,51,59,71]; [35,44,46,62,63,72,73]. PIP2 is an important recruiting factor, priming secretory vesicles for exocytosis, by interacting with several essential exocytic proteins [71].…”

Section: Pma-induced Exocytosis Of Mmp-9 Accompanied By Transient Recmentioning

confidence: 99%

Imaging the rapid yet transient accumulation of regulatory lipids, lipid kinases, and protein kinases during membrane fusion, at sites of exocytosis of MMP-9 in cancer cells

Stephens

Powell

Taraska

et al. 2020

Preprint

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Background: The control of exocytosis is physiologically essential. In vitro SNARE proteins are sufficient to drive membrane fusion, but in cells there are additional proteins and lipids that work together to drive efficient, fast, and timely release of secretory vesicle cargo. Growing evidence suggests that regulatory lipids act as important lipid signals and regulate various biological processes including exocytosis. Though functional roles of many of these regulatory lipids has been linked to exocytosis, the dynamic behavior of these lipids during membrane fusion at sites of exocytosis in cell culture remains unknown. Methods: We used total internal reflection fluorescence microscopy (TIRF) to observe the spatial organization and temporal dynamics of several lipids, and accessory proteins, like lipid kinases and protein kinases, in the form of protein kinase C (PRKC) relative to single sites of exocytosis of MMP-9 in living MCF-7 cancer cells. Results: After stimulating exocytosis with PMA, we observed a transient accumulation of the regulatory lipids (e.g. PIP, PIP2, and DAG), lipid kinases (e.g. PI4K2B, PI4K3A, and PIP5KA), and protein kinases (e.g. PRKCA and PRKCE) at exocytic sites centered on the time of membrane fusion, before rapidly diffusing away from the fusion sites. Additionally, the synthesis of these regulatory lipids, degradation of these lipids, and the downstream effectors activated by these lipids, are also achieved by the recruitment and accumulation of key enzymes at exocytic sites (during the moment of cargo release), including lipid kinases, protein kinases, and phospholipases that facilitate membrane fusion and exocytosis of MMP-9. Conclusions: This work suggests that these regulatory lipids and associated effector proteins are locally synthesized and/or recruited to exocytic sites, during the time of membrane fusion and cargo release, and their enrichment at fusion sites serves as an important spatial and temporal organizing “element” defining individual exocytic sites.

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Regulation of insulin exocytosis by calcium-dependent protein kinase C in beta cells

Cited by 38 publications

References 163 publications

The regulatory G protein signaling complex, Gβ5–R7, promotes glucose- and extracellular signal–stimulated insulin secretion

The regulatory G protein signaling complex, Gβ5–R7, promotes glucose- and extracellular signal–stimulated insulin secretion

Protein kinase Cε activation induces EHD-dependent degradation and downregulation of K_ATPchannels: Implications for glucose stimulated insulin secretion

Imaging the rapid yet transient accumulation of regulatory lipids, lipid kinases, and protein kinases during membrane fusion, at sites of exocytosis of MMP-9 in cancer cells

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Regulation of insulin exocytosis by calcium-dependent protein kinase C in beta cells

Cited by 38 publications

References 163 publications

The regulatory G protein signaling complex, Gβ5–R7, promotes glucose- and extracellular signal–stimulated insulin secretion

The regulatory G protein signaling complex, Gβ5–R7, promotes glucose- and extracellular signal–stimulated insulin secretion

Protein kinase Cε activation induces EHD-dependent degradation and downregulation of KATPchannels: Implications for glucose stimulated insulin secretion

Imaging the rapid yet transient accumulation of regulatory lipids, lipid kinases, and protein kinases during membrane fusion, at sites of exocytosis of MMP-9 in cancer cells

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Protein kinase Cε activation induces EHD-dependent degradation and downregulation of K_ATPchannels: Implications for glucose stimulated insulin secretion