scholarly journals Depolarizing bipolar cell dysfunction due to a Trpm1 point mutation

2012 ◽  
Vol 108 (9) ◽  
pp. 2442-2451 ◽  
Author(s):  
Neal S. Peachey ◽  
Jillian N. Pearring ◽  
Pasano Bojang ◽  
Matthew E. Hirschtritt ◽  
Gwen Sturgill-Short ◽  
...  
Keyword(s):  
Visual Processing ◽  
Bipolar Cells ◽  
Dominant Negative ◽  
Chemical Mutagenesis ◽  
Similar Reduction ◽  
Cell Dysfunction ◽  
Recessive Form ◽  
Key Factor ◽  
Depolarizing Bipolar Cell ◽  
Pore Domain

Mutations in TRPM1 are found in humans with an autosomal recessive form of complete congenital stationary night blindness (cCSNB). The Trpm1−/− mouse has been an important animal model for this condition. Here we report a new mouse mutant, tvrm27, identified in a chemical mutagenesis screen. Genetic mapping of the no b-wave electroretinogram (ERG) phenotype of tvrm27 localized the mutation to a chromosomal region that included Trpm1. Complementation testing with Trpm1−/− mice confirmed a mutation in Trpm1. Sequencing identified a nucleotide change in exon 23, converting a highly conserved alanine within the pore domain to threonine (p.A1068T). Consistent with prior studies of Trpm1−/− mice, no anatomical changes were noted in the Trpm1 tvrm27/tvrm27 retina. The Trpm1 tvrm27/tvrm27 phenotype is distinguished from that of Trpm1−/− by the retention of TRPM1 expression on the dendritic tips of depolarizing bipolar cells (DBCs). While ERG b-wave amplitudes of Trpm1+/− heterozygotes are comparable to wild type, those of Trpm1+/ tvrm27 mice are reduced by 32%. A similar reduction in the response of Trpm1+/ tvrm27 DBCs to LY341495 or capsaicin is evident in whole cell recordings. These data indicate that the p.A1068T mutant TRPM1 acts as a dominant negative with respect to TRPM1 channel function. Furthermore, these data indicate that the number of functional TRPM1 channels at the DBC dendritic tips is a key factor in defining DBC response amplitude. The Trpm1 tvrm27/tvrm27 mutant will be useful for elucidating the role of TRPM1 in DBC signal transduction, for determining how Trpm1 mutations impact central visual processing, and for evaluating experimental therapies for cCSNB.

fMRI-Guided TMS on Cortical Eye Fields: The Frontal But Not Intraparietal Eye Fields Regulate the Coupling Between Visuospatial Attention and Eye Movements

2009 ◽  
Vol 102 (6) ◽  
pp. 3469-3480 ◽  
Author(s):  
H. M. Van Ettinger-Veenstra ◽  
W. Huijbers ◽  
T. P. Gutteling ◽  
M. Vink ◽  
J. L. Kenemans ◽  
...  
Keyword(s):  
Visual Cortex ◽  
Eye Movements ◽  
Visual Processing ◽  
Discrimination Performance ◽  
Visual Image ◽  
Single Pulse ◽  
Visuospatial Attention ◽  
Movement Direction ◽  
Key Factor ◽  
And Shifts

It is well known that parts of a visual scene are prioritized for visual processing, depending on the current situation. How the CNS moves this focus of attention across the visual image is largely unknown, although there is substantial evidence that preparation of an action is a key factor. Our results support the view that direct corticocortical feedback connections from frontal oculomotor areas to the visual cortex are responsible for the coupling between eye movements and shifts of visuospatial attention. Functional magnetic resonance imaging (fMRI)–guided transcranial magnetic stimulation (TMS) was applied to the frontal eye fields (FEFs) and intraparietal sulcus (IPS). A single pulse was delivered 60, 30, or 0 ms before a discrimination target was presented at, or next to, the target of a saccade in preparation. Results showed that the known enhancement of discrimination performance specific to locations to which eye movements are being prepared was enhanced by early TMS on the FEF contralateral to eye movement direction, whereas TMS on the IPS resulted in a general performance increase. The current findings indicate that the FEF affects selective visual processing within the visual cortex itself through direct feedback projections.

scholarly journals Sensing through Non-Sensing Ocular Ion Channels

2020 ◽  
Vol 21 (18) ◽  
pp. 6925
Author(s):  
Meha Kabra ◽  
Bikash Ranjan Pattnaik
Keyword(s):  
Ion Channels ◽  
Visual Processing ◽  
Signal Transmission ◽  
Dominant Negative ◽  
Dominant Negative Effect ◽  
Cone Dystrophy ◽  
Wide Range ◽  
The Impact

Ion channels are membrane-spanning integral proteins expressed in multiple organs, including the eye. In the eye, ion channels are involved in various physiological processes, like signal transmission and visual processing. A wide range of mutations have been reported in the corresponding genes and their interacting subunit coding genes, which contribute significantly to an array of blindness, termed ocular channelopathies. These mutations result in either a loss- or gain-of channel functions affecting the structure, assembly, trafficking, and localization of channel proteins. A dominant-negative effect is caused in a few channels formed by the assembly of several subunits that exist as homo- or heteromeric proteins. Here, we review the role of different mutations in switching a “sensing” ion channel to “non-sensing,” leading to ocular channelopathies like Leber’s congenital amaurosis 16 (LCA16), cone dystrophy, congenital stationary night blindness (CSNB), achromatopsia, bestrophinopathies, retinitis pigmentosa, etc. We also discuss the various in vitro and in vivo disease models available to investigate the impact of mutations on channel properties, to dissect the disease mechanism, and understand the pathophysiology. Innovating the potential pharmacological and therapeutic approaches and their efficient delivery to the eye for reversing a “non-sensing” channel to “sensing” would be life-changing.

scholarly journals The Death Domain Kinase RIP Is Essential for TRAIL (Apo2L)-Induced Activation of IκB Kinase and c-Jun N-Terminal Kinase

2000 ◽  
Vol 20 (18) ◽  
pp. 6638-6645 ◽  
Author(s):  
Yong Lin ◽  
Anne Devin ◽  
Amy Cook ◽  
Maccon M. Keane ◽  
Michelle Kelliher ◽  
...  
Keyword(s):  
Ectopic Expression ◽  
Dominant Negative ◽  
Dominant Negative Mutant ◽  
Death Domain ◽  
Iκb Kinase ◽  
Tnf Superfamily ◽  
Key Factor ◽  
Induced Apoptosis ◽  
Jnk Activation ◽  
Necrosis Factor

ABSTRACT Tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL) (Apo2 ligand [Apo2L]) is a member of the TNF superfamily and has been shown to have selective antitumor activity. Although it is known that TRAIL (Apo2L) induces apoptosis and activates NF-κB and Jun N-terminal kinase (JNK) through receptors such as TRAIL-R1 (DR4) and TRAIL-R2 (DR5), the components of its signaling cascade have not been well defined. In this report, we demonstrated that the death domain kinase RIP is essential for TRAIL-induced IκB kinase (IKK) and JNK activation. We found that ectopic expression of the dominant negative mutant RIP, RIP(559–671), blocks TRAIL-induced IKK and JNK activation. In the RIP null fibroblasts, TRAIL failed to activate IKK and only partially activated JNK. The endogenous RIP protein was detected by immunoprecipitation in the TRAIL-R1 complex after TRAIL treatment. More importantly, we found that RIP is not involved in TRAIL-induced apoptosis. In addition, we also demonstrated that the TNF receptor-associated factor 2 (TRAF2) plays little role in TRAIL-induced IKK activation although it is required for TRAIL-mediated JNK activation. These results indicated that the death domain kinase RIP, a key factor in TNF signaling, also plays a pivotal role in TRAIL-induced IKK and JNK activation.

Pharmacological analysis of the rat cone electroretinogram

2003 ◽  
Vol 20 (3) ◽  
pp. 297-306 ◽  
Author(s):  
LI XU ◽  
SHERRY L. BALL ◽  
KENNETH R. ALEXANDER ◽  
NEAL S. PEACHEY
Keyword(s):  
Retinal Disease ◽  
Experimental Treatment ◽  
Negative Polarity ◽  
Bipolar Cells ◽  
Sprague Dawley ◽  
Negative Wave ◽  
Sprague Dawley Rats ◽  
Amplitude Component ◽  
Cone System ◽  
Depolarizing Bipolar Cell

The electroretinogram (ERG) of the cone system provides a useful noninvasive measure of the activity of the cone pathway. Despite a wide application of the cone ERG in the study of rodent models of human hereditary retinal disease, the cellular origins of the rat cone ERG have not been well defined. Here, we address this issue using a pharmacological approach that has been used previously to derive ERG response components. Agents that impair synaptic transmission at well-defined retinal loci were dissolved in saline and injected into the vitreous of adult Sprague-Dawley rats anesthetized with ketamine/xylazine, and cone ERGs were recorded approximately 2 h later. Analysis of the resulting waveforms indicated that the rat cone ERG includes a relatively small-amplitude component of negative polarity that is derived from the activity of cone photoreceptors, and perhaps retinal glial (Müller) cells. The cone depolarizing bipolar cell pathway contributes a positive potential of large amplitude to the rat cone ERG. In comparison, the contribution of hyperpolarizing bipolar cells is of negative polarity and of much smaller amplitude. The inner retina contributes a negative wave upon which higher frequency oscillations are superimposed. These results provide a foundation for interpreting changes in the waveform of the rat cone ERG that may be observed following genetic alteration or other experimental treatment.

A role for 5HT3 receptors in visual processing in the mammalian retina

1993 ◽  
Vol 10 (3) ◽  
pp. 511-522 ◽  
Author(s):  
William J. Brunken ◽  
Xiao-Tao Jin
Keyword(s):  
Visual Processing ◽  
Ganglion Cells ◽  
Cell Activity ◽  
Phosphatidyl Inositol ◽  
Amacrine Cells ◽  
Bipolar Cells ◽  
Reciprocal Effect ◽  
Mammalian Retina ◽  
Messenger System

AbstractWe investigated the role of 5HT3 receptors in the mammalian retina using electrophysiological techniques to monitor ganglion cell activity. Activation of 5HT3 receptors with the selective agonist 1-phenylbiguanide (PBG) increased the ON responses of ON-center ganglion cells, while decreasing the OFF responses of OFF-center cells. The application of a selective 5HT3 antagonist had a reciprocal effect, namely it reduced the center response in ON-center cells and concomitantly increased the center responses in OFF-center cells. Since putative serotoninergic amacrine cells in the retina are connected specifically to the rod bipolar cell, these agents most likely affect the rod bipolar terminal. These data, together with previous studies, suggest that both 5HT2 and 5HT3 receptors mediate an excitatory influence which serves to facilitate the output from rod bipolar cells, the former via a phosphatidyl inositol second-messenger system, and the latter via a direction channel.

scholarly journals TRESK and TREK-2 two-pore-domain potassium channel subunits form functional heterodimers in primary somatosensory neurons

2020 ◽  
Vol 295 (35) ◽  
pp. 12408-12425 ◽  
Author(s):  
Miklós Lengyel ◽  
Gábor Czirják ◽  
David A. Jacobson ◽  
Péter Enyedi
Keyword(s):  
Sensory Neurons ◽  
Single Channel ◽  
Potassium Conductance ◽  
Dominant Negative ◽  
Resting Membrane Potential ◽  
Pharmacological Properties ◽  
Primary Sensory Neurons ◽  
Somatosensory Neurons ◽  
Covalently Linked ◽  
Pore Domain

Two-pore-domain potassium channels (K2P) are the major determinants of the background potassium conductance. They play a crucial role in setting the resting membrane potential and regulating cellular excitability. These channels form homodimers; however, a few examples of heterodimerization have also been reported. The K2P channel subunits TRESK and TREK-2 provide the predominant background potassium current in the primary sensory neurons of the dorsal root and trigeminal ganglia. A recent study has shown that a TRESK mutation causes migraine because it leads to the formation of a dominant negative truncated TRESK fragment. Surprisingly, this fragment can also interact with TREK-2. In this study, we determined the biophysical and pharmacological properties of the TRESK/TREK-2 heterodimer using a covalently linked TRESK/TREK-2 construct to ensure the assembly of the different subunits. The tandem channel has an intermediate single-channel conductance compared with the TRESK and TREK-2 homodimers. Similar conductance values were recorded when TRESK and TREK-2 were coexpressed, demonstrating that the two subunits can spontaneously form functional heterodimers. The TRESK component confers calcineurin-dependent regulation to the heterodimer and gives rise to a pharmacological profile similar to the TRESK homodimer, whereas the presence of the TREK-2 subunit renders the channel sensitive to the selective TREK-2 activator T2A3. In trigeminal primary sensory neurons, we detected single-channel activity with biophysical and pharmacological properties similar to the TRESK/TREK-2 tandem, indicating that WT TRESK and TREK-2 subunits coassemble to form functional heterodimeric channels also in native cells.

scholarly journals Mutations Affecting the Ability of theEscherichia coli UmuD′ Protein To Participate in SOS Mutagenesis

1999 ◽  
Vol 181 (1) ◽  
pp. 177-185 ◽  
Author(s):  
Toshihiro Ohta ◽  
Mark D. Sutton ◽  
Angelina Guzzo ◽  
Shannon Cole ◽  
Ann E. Ferentz ◽  
...  
Keyword(s):  
Translesion Synthesis ◽  
Dominant Negative ◽  
Chemical Mutagenesis ◽  
Dominant Negative Effect ◽  
Multicopy Plasmid ◽  
Uv Mutagenesis ◽  
Synthesis Mechanism ◽  
Negative Effect ◽  
Conserved Residue

The products of the SOS-regulated umuDC operon are required for most UV and chemical mutagenesis in Escherichia coli, a process that results from a translesion synthesis mechanism. The UmuD protein is activated for its role in mutagenesis by a RecA-facilitated autodigestion that removes the N-terminal 24 amino acids. A previous genetic screen for nonmutable umuDmutants had resulted in the isolation of a set of missense mutants that produced UmuD proteins that were deficient in RecA-mediated cleavage (J. R. Battista, T. Ohta, T. Nohmi, W. Sun, and G. C. Walker, Proc. Natl. Acad. Sci. USA 87:7190–7194, 1990). To identify elements of the UmuD′ protein necessary for its role in translesion synthesis, we began with umuD′, a modified form of theumuD gene that directly encodes the UmuD′ protein, and obtained missense umuD′ mutants deficient in UV and methyl methanesulfonate mutagenesis. The D39G, L40R, and T51I mutations affect residues located at the UmuD′2 homodimer interface and interfere with homodimer formation in vivo. The D75A mutation affects a highly conserved residue located at one end of the central strand in a three-stranded β-sheet and appears to interfere with UmuD′2 homodimer formation indirectly by affecting the structure of the UmuD′ monomer. When expressed from a multicopy plasmid, the L40R umuD′ mutant gene exhibited a dominant negative effect on a chromosomal umuD + gene with respect to UV mutagenesis, suggesting that the mutation has an effect on UmuD′ function that goes beyond its impairment of homodimer formation. The G129D mutation affects a highly conserved residue that lies at the end of the long C-terminal β-strand and results in a mutant UmuD′ protein that exhibits a strongly dominant negative effect on UV mutagenesis in a umuD +strain. The A30V and E35K mutations alter residues in the N-terminal arms of the UmuD′2 homodimer, which are mobile in solution.

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