scholarly journals PKCα-dependent interaction of otoferlin and calbindin: evidence for regulation of endocytosis in inner hair cells

2019 ◽  
Author(s):  
Andreia P. Cepeda ◽  
Hanan Al-Moyed ◽  
Christof Lenz ◽  
Henning Urlaub ◽  
Ellen Reisinger
Keyword(s):  
Hair Cell ◽  
Serine Phosphorylation ◽  
Dependent Manner ◽  
Myosin Vi ◽  
Inner Hair Cell ◽  
Signaling Complex ◽  
Calbindin D28k ◽  
Vesicle Cycle ◽  
Activity Dependent

AbstractOtoferlin is essential for the fast and indefatigable release of synaptic vesicles at auditory inner hair cell (IHC) ribbon synapses, being involved in exocytic, endocytic and regenerative steps of the synaptic vesicle cycle. Serving diverse functions at this highly dynamic synapse implies that this multi-C2 domain protein is precisely regulated. Here we found protein kinase C α (PKCα) and otoferlin to colocalize in endocytic recycling compartments upon IHC depolarization and to interact in an activity-dependent manner. In vitro assays confirmed that PKCα can phosphorylate otoferlin at five serine residues, which correlates with increased serine phosphorylation in <40 nm proximity to otoferlin in murine IHCs that can be fully blocked by combining PKC and CaMKII inhibitors. Moreover, otoferlin interacts with calbindin-D28k in stimulated IHCs, which was precluded when PKCα was inhibited. Similarly, the activity-dependent increase in otoferlin-myosin VI interaction depends on PKCα activation. We propose that upon strong hair cell depolarization, PKCα phosphorylates otoferlin, thereby enabling it to interact with calbindin-D28k and myosin VI, building a Ca2+-dependent signaling complex that possibly regulates different modes of endocytosis.

Platelet-derived growth factor (PDGF)-dependent association of phospholipase C-gamma with the PDGF receptor signaling complex

1990 ◽  
Vol 10 (5) ◽  
pp. 2359-2366
Author(s):  
D K Morrison ◽  
D R Kaplan ◽  
S G Rhee ◽  
L T Williams
Keyword(s):  
Growth Factor ◽  
Tyrosine Phosphorylation ◽  
Serine Phosphorylation ◽  
Platelet Derived Growth Factor ◽  
Pdgf Receptor ◽  
Wild Type ◽  
Receptor Proteins ◽  
Signaling Complex

We investigated the interaction of phospholipase C-gamma (PLC-gamma) with wild-type and mutant forms of the platelet-derived growth factor (PDGF) beta-receptor both in vivo and in vitro. After PDGF treatment of CHO cell lines expressing wild-type or either of two mutant (delta Ki and Y825F) PDGF receptors, PLC-gamma became tyrosine phosphorylated and associated with the receptor proteins. The receptor association and tyrosine phosphorylation of PLC-gamma correlated with the ability of these receptors to mediate ligand-induced phosphatidylinositol turnover. However, both the delta Ki and Y825F mutant receptors were deficient in transmitting mitogenic signals, suggesting that the PDGF-induced tyrosine phosphorylation and receptor association of PLC-gamma are not sufficient to account for the growth-stimulatory activity of PDGF. Wild-type and delta Ki mutant PDGF receptor proteins expressed with recombinant baculovirus vectors also associated in vitro with mammalian PLC-gamma. However, baculovirus-expressed c-fms, v-fms, c-src, and Raf-1 proteins failed to associate with PLC-gamma under similar conditions. Phosphatase treatment of the baculovirus-expressed PDGF receptor greatly decreased its association with PLC-gamma. This requirement for receptor phosphorylation was also observed in vivo, where PLC-gamma could not associate with a mutant PDGF receptor (K602A) defective in autophosphorylation. PLC-gamma also coimmunoprecipitated with two other putative receptor substrates, the serine-threonine kinase Raf-1 and the 85-kilodalton phosphatidylinositol-3' kinase, presumably through its association with the ligand-activated receptor. Furthermore, baculovirus-expressed Raf-1 phosphorylated purified PLC-gamma in vitro at sites which showed increased serine phosphorylation in vivo in response to PDGF. These results suggest that PDGF directly influences PLC activity by inducing the association of PLC-gamma with a receptor signaling complex, resulting in increased tyrosine and serine phosphorylation of PLC-gamma.

scholarly journals An XA21-Associated Kinase (OsSERK2) regulates immunity mediated by the XA21 and XA3 immune receptors

2013 ◽  
Author(s):  
Xuewei Chen ◽  
Shimin Zuo ◽  
Benjamin Schwessinger ◽  
Mawsheng Chern ◽  
Patrick Canlas ◽  
...  
Keyword(s):  
Direct Interaction ◽  
Dependent Manner ◽  
Receptor Kinase ◽  
Immune Receptor ◽  
Immune Receptors ◽  
Yeast Two Hybrid System ◽  
Intracellular Domains ◽  
Activity Dependent

The rice XA21 immune receptor kinase and the structurally related XA3 receptor, confer immunity to Xanthomonas oryzae pv. oryzae (Xoo), the causal agent of bacterial leaf blight. Here we report the isolation of OsSERK2 (rice somatic embryogenesis receptor kinase 2) and demonstrate that OsSERK2 positively regulates immunity mediated by XA21 and XA3 as well as the rice immune receptor FLS2 (OsFLS2). Rice plants silenced for OsSerk2 display altered morphology and reduced sensitivity to the hormone brassinolide. OsSERK2 interacts with the intracellular domains of each immune receptor in the yeast-two-hybrid system in a kinase activity dependent manner. OsSERK2 undergoes bidirectional trans-phosphorylation with XA21 in vitro and forms a constitutive complex with XA21 in vivo. Taken together, these results demonstrate an essential role for OsSERK2 in the function of three rice immune receptors and suggest that direct interaction with the rice immune receptors is critical for their function.

scholarly journals Myosin VI is required for the proper maturation and function of inner hair cell ribbon synapses

2009 ◽  
Vol 18 (23) ◽  
pp. 4615-4628 ◽  
Author(s):  
Isabelle Roux ◽  
Suzanne Hosie ◽  
Stuart L. Johnson ◽  
Amel Bahloul ◽  
Nadège Cayet ◽  
...  
Keyword(s):  
Hair Cell ◽  
Myosin Vi ◽  
Inner Hair Cell ◽  
Ribbon Synapses ◽  
And Function

scholarly journals Phosphorylation of Connexin36 near the C-terminus switches binding affinities for PDZ-domain and 14–3–3 proteins in vitro

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Stephan Tetenborg ◽  
Helen Y. Wang ◽  
Lena Nemitz ◽  
Anne Depping ◽  
Alexsandra B. Espejo ◽  
...  
Keyword(s):  
Gap Junctions ◽  
Binding Affinity ◽  
Protein Microarray ◽  
Pdz Domain ◽  
Phosphorylation Site ◽  
Binding Domain ◽  
Dependent Manner ◽  
C Terminus ◽  
Activity Dependent

Abstract Connexin36 (Cx36) is the most abundant connexin in central nervous system neurons. It forms gap junction channels that act as electrical synapses. Similar to chemical synapses, Cx36-containing gap junctions undergo activity-dependent plasticity and complex regulation. Cx36 gap junctions represent multimolecular complexes and contain cytoskeletal, regulatory and scaffolding proteins, which regulate channel conductance, assembly and turnover. The amino acid sequence of mammalian Cx36 harbors a phosphorylation site for the Ca2+/calmodulin-dependent kinase II at serine 315. This regulatory site is homologous to the serine 298 in perch Cx35 and in close vicinity to a PDZ binding domain at the very C-terminal end of the protein. We hypothesized that this phosphorylation site may serve as a molecular switch, influencing the affinity of the PDZ binding domain for its binding partners. Protein microarray and pulldown experiments revealed that this is indeed the case: phosphorylation of serine 298 decreased the binding affinity for MUPP1, a known scaffolding partner of connexin36, and increased the binding affinity for two different 14–3–3 proteins. Although we did not find the same effect in cell culture experiments, our data suggest that phosphorylation of serine 315/298 may serve to recruit different proteins to connexin36/35-containing gap junctions in an activity-dependent manner.

scholarly journals TRIM39 deficiency inhibits tumor progression and autophagic flux in colorectal cancer via suppressing the activity of Rab7

2021 ◽  
Vol 12 (4) ◽  
Author(s):  
Jia Hu ◽  
Xueliang Ding ◽  
Shaobo Tian ◽  
Yanan Chu ◽  
Zhibo Liu ◽  
...  
Keyword(s):  
Colorectal Cancer ◽  
Autophagic Flux ◽  
Dependent Manner ◽  
Functional Studies ◽  
Normal Tissues ◽  
Tumor Tissues ◽  
Autophagic Degradation ◽  
Activity Dependent

AbstractThe biological function of TRIM39, a member of TRIM family, remains largely unexplored in cancer, especially in colorectal cancer (CRC). In this study, we show that TRIM39 is upregulated in tumor tissues compared to adjacent normal tissues and associated with poor prognosis in CRC. Functional studies demonstrate that TRIM39 deficiency restrains CRC progression in vitro and in vivo. Our results further find that TRIM39 is a positive regulator of autophagosome–lysosome fusion. Mechanistically, TRIM39 interacts with Rab7 and promotes its activity via inhibiting its ubiquitination at lysine 191 residue. Depletion of TRIM39 inhibits CRC progression and autophagic flux in a Rab7 activity-dependent manner. Moreover, TRIM39 deficiency suppresses CRC progression through inhibiting autophagic degradation of p53. Thus, our findings uncover the roles as well as the relevant mechanisms of TRIM39 in CRC and establish a functional relationship between autophagy and CRC progression, which may provide promising approaches for the treatment of CRC.

scholarly journals Two systems in vitro that show insulin-stimulated serine kinase activity towards the insulin receptor

1988 ◽  
Vol 250 (2) ◽  
pp. 509-519 ◽  
Author(s):  
D M Smith ◽  
M J King ◽  
G J Sale
Keyword(s):  
Insulin Receptor ◽  
Wheat Germ Agglutinin ◽  
Wheat Germ ◽  
Kinase Activity ◽  
Serine Phosphorylation ◽  
Dependent Manner ◽  
Serine Kinase ◽  
Two Systems ◽  
32P Incorporation

Two systems in vitro are described that show insulin-stimulated phosphorylation of the insulin receptor on serine residues. In the first system, insulin receptor was purified partially from Fao rat hepatoma cells by direct solubilization of the cells in Triton X-100 and chromatography on wheat-germ-agglutinin-agarose. Phosphorylation of these preparations with [gamma-32P]ATP in the presence or absence of insulin resulted in 32P incorporation exclusively into phosphotyrosine residues. Serine kinase activity towards the insulin receptor was reconstituted by adding extracts of Fao cells. Prior exposure of the cells to insulin stimulated serine kinase activity towards the insulin receptor in extracts 7.2-fold. A receptor serine kinase activity enhanced by treatment of cells with cyclic AMP analogues was also retained in the reconstituted system. In the second system, insulin receptor and insulin-sensitive serine kinase activity towards the insulin receptor were co-purified from human placenta. The protocol involved preparation of membranes, before solubilization and chromatography on wheat-germ-agglutinin-agarose, by using gentle procedures designed not to disrupt a potentially labile association between the insulin receptor and the serine kinase. Serine kinase activity in these preparations towards the insulin receptor was stimulated up to 10-fold by insulin, and the stoicheiometry of serine phosphorylation was estimated to be approx 0.8 mol/mol of insulin receptor for phosphorylations performed in the presence of insulin. Thus a preparation of insulin receptor is described for the first time that is phosphorylated to high stoicheiometry on serine in an insulin-dependent manner. Conditions that facilitate recovery and assay of serine kinase activity are defined and discussed. These systems provide a basis for characterizing the nature of the insulin-sensitive serine kinase that phosphorylates the insulin receptor, and defining its role in insulin action and control of receptor function.

scholarly journals Regulation of Raf-1 and Raf-1 mutants by Ras-dependent and Ras-independent mechanisms in vitro.

1995 ◽  
Vol 15 (8) ◽  
pp. 4125-4135 ◽  
Author(s):  
P Dent ◽  
D B Reardon ◽  
D K Morrison ◽  
T W Sturgill
Keyword(s):  
Protein Kinase ◽  
Plasma Membranes ◽  
De Novo ◽  
Serine Phosphorylation ◽  
Mitogen Activated Protein Kinase ◽  
Significant Activity ◽  
Dependent Manner ◽  
Wild Type ◽  
Independent Manner

The serine/threonine kinase Raf-1 functions downstream from Ras to activate mitogen-activated protein kinase kinase, but the mechanisms of Raf-1 activation are incompletely understood. To dissect these mechanisms, wild-type and mutant Raf-1 proteins were studied in an in vitro system with purified plasma membranes from v-Ras- and v-Src-transformed cells (transformed membranes). Wild-type (His)6- and FLAG-Raf-1 were activated in a Ras- and ATP-dependent manner by transformed membranes; however, Raf-1 proteins that are kinase defective (K375M), that lack an in vivo site(s) of regulatory tyrosine (YY340/341FF) or constitutive serine (S621A) phosphorylation, that do not bind Ras (R89L), or that lack an intact zinc finger (CC165/168SS) were not. Raf-1 proteins lacking putative regulatory sites for an unidentified kinase (S259A) or protein kinase C (S499A) were activated but with apparently reduced efficiency. The kinase(s) responsible for activation by Ras or Src may reside in the plasma membrane, since GTP loading of plasma membranes from quiescent NIH 3T3 cells (parental membranes) induced de novo capacity to activate Raf-1. Wild-type Raf-1, possessing only basal activity, was not activated by parental membranes in the absence of GTP loading. In contrast, Raf-1 Y340D, possessing significant activity, was, surprisingly, stimulated by parental membranes in a Ras-independent manner. The results suggest that activation of Raf-1 by phosphorylation may be permissive for further modulation by another membrane factor, such as a lipid. A factor(s) extracted with methanol-chloroform from transformed membranes or membranes from Sf9 cells coexpressing Ras and SrcY527F significantly enhanced the activity of Raf-1 Y340D or active Raf-1 but not that of inactive Raf-1. Our findings suggest a model for activation of Raf-1, wherein (i) Raf-1 associates with Ras-GTP, (ii) Raf-1 is activated by tyrosine and/or serine phosphorylation, and (iii) Raf-1 activity is further increased by a membrane cofactor.

scholarly journals Platelet-derived growth factor (PDGF)-dependent association of phospholipase C-gamma with the PDGF receptor signaling complex.

1990 ◽  
Vol 10 (5) ◽  
pp. 2359-2366 ◽  
Author(s):  
D K Morrison ◽  
D R Kaplan ◽  
S G Rhee ◽  
L T Williams
Keyword(s):  
Growth Factor ◽  
Tyrosine Phosphorylation ◽  
Serine Phosphorylation ◽  
Platelet Derived Growth Factor ◽  
Pdgf Receptor ◽  
Wild Type ◽  
Receptor Proteins ◽  
Signaling Complex

We investigated the interaction of phospholipase C-gamma (PLC-gamma) with wild-type and mutant forms of the platelet-derived growth factor (PDGF) beta-receptor both in vivo and in vitro. After PDGF treatment of CHO cell lines expressing wild-type or either of two mutant (delta Ki and Y825F) PDGF receptors, PLC-gamma became tyrosine phosphorylated and associated with the receptor proteins. The receptor association and tyrosine phosphorylation of PLC-gamma correlated with the ability of these receptors to mediate ligand-induced phosphatidylinositol turnover. However, both the delta Ki and Y825F mutant receptors were deficient in transmitting mitogenic signals, suggesting that the PDGF-induced tyrosine phosphorylation and receptor association of PLC-gamma are not sufficient to account for the growth-stimulatory activity of PDGF. Wild-type and delta Ki mutant PDGF receptor proteins expressed with recombinant baculovirus vectors also associated in vitro with mammalian PLC-gamma. However, baculovirus-expressed c-fms, v-fms, c-src, and Raf-1 proteins failed to associate with PLC-gamma under similar conditions. Phosphatase treatment of the baculovirus-expressed PDGF receptor greatly decreased its association with PLC-gamma. This requirement for receptor phosphorylation was also observed in vivo, where PLC-gamma could not associate with a mutant PDGF receptor (K602A) defective in autophosphorylation. PLC-gamma also coimmunoprecipitated with two other putative receptor substrates, the serine-threonine kinase Raf-1 and the 85-kilodalton phosphatidylinositol-3' kinase, presumably through its association with the ligand-activated receptor. Furthermore, baculovirus-expressed Raf-1 phosphorylated purified PLC-gamma in vitro at sites which showed increased serine phosphorylation in vivo in response to PDGF. These results suggest that PDGF directly influences PLC activity by inducing the association of PLC-gamma with a receptor signaling complex, resulting in increased tyrosine and serine phosphorylation of PLC-gamma.

scholarly journals Neuronal Activity-Induced BRG1 Phosphorylation Regulates Enhancer Activation

2020 ◽  
Author(s):  
Bongwoo Kim ◽  
Yi Luo ◽  
Xiaoming Zhan ◽  
Zilai Zhang ◽  
Xuanming Shi ◽  
...  
Keyword(s):  
Rna Polymerase Ii ◽  
Chromatin Remodeling ◽  
Neuronal Activity ◽  
Phosphorylation Site ◽  
Serine Phosphorylation ◽  
Dependent Manner ◽  
Enhancer Rna ◽  
Induce Activity ◽  
Chromatin Remodeling Complexes ◽  
Activity Dependent

SUMMARYNeuronal activity-induced enhancers drive the gene induction in response to stimulation. Here, we demonstrate that BRG1, the core subunit of SWI/SNF-like BAF ATP-dependent chromatin remodeling complexes, regulates neuronal activity-induced enhancers. Upon stimulation, BRG1 is recruited to enhancers in an H3K27Ac-dependent manner. BRG1 regulates enhancer basal activities and inducibility by affecting cohesin binding, enhancer-promoter looping, RNA polymerase II recruitment, and enhancer RNA expression. Furthermore, we identified a serine phosphorylation site in BRG1 that is induced by neuronal activities and is sensitive to CaMKII inhibition. BRG1 phosphorylation affects its interaction with several transcription co-factors, possibly modulating BRG1 mediated transcription outcomes. Using mice with knock-in mutations, we showed that non-phosphorylatable BRG1 fails to efficiently induce activity-dependent genes, whereas phosphomimic BRG1 increases the enhancer activities and inducibility. These mutant mice displayed anxiety-like phenotypes and altered responses to stress. Therefore, our data reveal a mechanism connecting neuronal signaling to enhancer activities through BRG1 phosphorylation.

scholarly journals Complement membrane attack complexes activate noncanonical NF-κB by forming an Akt+NIK+ signalosome on Rab5+ endosomes

2015 ◽  
Vol 112 (31) ◽  
pp. 9686-9691 ◽  
Author(s):  
Dan Jane-wit ◽  
Yulia V. Surovtseva ◽  
Lingfeng Qin ◽  
Guangxin Li ◽  
Rebecca Liu ◽  
...  
Keyword(s):  
Endothelial Cells ◽  
Dependent Manner ◽  
Sirna Screen ◽  
Akt Activation ◽  
Signaling Complex ◽  
Iκb Kinase ◽  
Genome Wide ◽  
A Genome

Complement membrane attack complexes (MACs) promote inflammatory functions in endothelial cells (ECs) by stabilizing NF-κB–inducing kinase (NIK) and activating noncanonical NF-κB signaling. Here we report a novel endosome-based signaling complex induced by MACs to stabilize NIK. We found that, in contrast to cytokine-mediated activation, NIK stabilization by MACs did not involve cIAP2 or TRAF3. Informed by a genome-wide siRNA screen, instead this response required internalization of MACs in a clathrin-, AP2-, and dynamin-dependent manner into Rab5+endosomes, which recruited activated Akt, stabilized NIK, and led to phosphorylation of IκB kinase (IKK)-α. Active Rab5 was required for recruitment of activated Akt to MAC+ endosomes, but not for MAC internalization or for Akt activation. Consistent with these in vitro observations, MAC internalization occurred in human coronary ECs in vivo and was similarly required for NIK stabilization and EC activation. We conclude that MACs activate noncanonical NF-κB by forming a novel Akt+NIK+ signalosome on Rab5+ endosomes.

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