scholarly journals mGluR6 deletion renders the TRPM1 channel in retina inactive

2012 ◽  
Vol 107 (3) ◽  
pp. 948-957 ◽  
Author(s):  
Ying Xu ◽  
Anuradha Dhingra ◽  
Marie E. Fina ◽  
Chieko Koike ◽  
Takahisa Furukawa ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
G Protein ◽  
Transient Receptor Potential ◽  
Metabotropic Glutamate Receptor ◽  
Receptor Potential ◽  
Bipolar Cells ◽  
Wild Type ◽  
Protein Subunit ◽  
Transient Receptor Potential Melastatin ◽  
Rod Bipolar Cells

In darkness, glutamate released from photoreceptors activates the metabotropic glutamate receptor 6 (mGluR6) on retinal ON bipolar cells. This activates the G protein Go, which then closes transient receptor potential melastatin 1 (TRPM1) channels, leading to cells' hyperpolarization. It has been generally assumed that deleting mGluR6 would render the cascade inactive and the ON bipolar cells constitutively depolarized. Here we show that the rod bipolar cells in mGluR6-null mice were hyperpolarized. The slope conductance of the current-voltage curves and the current noise were smaller than in wild type. Furthermore, while in wild-type rod bipolar cells, TRPM1 could be activated by local application of capsaicin; in null cells, it did not. These results suggest that the TRPM1 channel in mGluR6-null rod bipolar cells is inactive. To explore the reason for this lack of activity, we tested if mGluR6 deletion affected expression of cascade components. Immunostaining for G protein subunit candidates Gαo, Gβ3, and Gγ13 showed no significant changes in their expression or distribution. Immunostaining for TRPM1 in the dendritic tips was greatly reduced, but the channel was still present in the soma and primary dendrites of mGluR6-null bipolar cells, where a certain fraction of TRPM1 appears to localize to the plasma membrane. Consequently, the lack of TRPM1 activity in the null retina is unlikely to be due to failure of the channels to localize to the plasma membrane. We speculate that, to be constitutively active, TRPM1 channels in ON bipolar cells have to be in a complex, or perhaps require an unidentified factor.

Glycosylation of the osmoresponsive transient receptor potential channel TRPV4 on Asn-651 influences membrane trafficking

2006 ◽  
Vol 290 (5) ◽  
pp. F1103-F1109 ◽  
Author(s):  
Hongshi Xu ◽  
Yi Fu ◽  
Wei Tian ◽  
David M. Cohen
Keyword(s):  
Plasma Membrane ◽  
Membrane Trafficking ◽  
Transient Receptor Potential ◽  
Receptor Potential ◽  
Trp Channel ◽  
Hek293 Cells ◽  
Wild Type ◽  
Functional Feature ◽  
Voltage Gated ◽  
Transient Receptor

We identified a consensus N-linked glycosylation motif within the pore-forming loop between the fifth and sixth transmembrane segments of the osmoresponsive transient receptor potential (TRP) channel TRPV4. Mutation of this residue from Asn to Gln (i.e., TRPV4N651Q) resulted in loss of a slower migrating band on anti-TRPV4 immunoblots and a marked reduction in lectin-precipitable TRPV4 immunoreactivity. HEK293 cells transiently transfected with the mutant TRPV4N651Q exhibited increased calcium entry in response to hypotonic stress relative to wild-type TRPV4 transfectants. This increase in hypotonicity responsiveness was associated with an increase in plasma membrane targeting of TRPV4N651Q relative to wild-type TRPV4 in both HEK293 and COS-7 cells but had no effect on overall channel abundance in whole cell lysates. Residue N651 of TRPV4 is immediately adjacent to the pore-forming loop. Although glycosylation in this vicinity has not been reported for a TRP channel, the structurally related hexahelical hyperpolarization-activated cyclic nucleotide-gated channel, HCN2, and the voltage-gated potassium channel, human ether-a-go-go-related (HERG), share a nearly identically situated and experimentally confirmed N-linked glycosylation site which promotes rather than limits channel insertion into the plasma membrane. These data point to a potentially conserved structural and functional feature influencing membrane trafficking across diverse members of the voltage-gated-like ion channel superfamily.

scholarly journals Transient Receptor Potential Melastatin 1 (TRPM1) Is an Ion-conducting Plasma Membrane Channel Inhibited by Zinc Ions

2011 ◽  
Vol 286 (14) ◽  
pp. 12221-12233 ◽  
Author(s):  
Sachar Lambert ◽  
Anna Drews ◽  
Oleksandr Rizun ◽  
Thomas F. J. Wagner ◽  
Annette Lis ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Transient Receptor Potential ◽  
Receptor Potential ◽  
Zinc Ions ◽  
Membrane Channel ◽  
Transient Receptor Potential Melastatin ◽  
Ion Conducting ◽  
Transient Receptor

scholarly journals The G protein-biased PZM21 and TRV130 act as partial agonists of μ-opioid receptors signaling to ion channel targets

2018 ◽  
Author(s):  
Yevgen Yudin ◽  
Tibor Rohacs
Keyword(s):  
Ion Channels ◽  
Ion Channel ◽  
G Protein ◽  
Opioid Receptors ◽  
Transient Receptor Potential ◽  
Receptor Potential ◽  
Partial Agonists ◽  
Transient Receptor Potential Melastatin ◽  
Transient Receptor ◽  
Μ Opioid Receptors

Opioids exert many of their acute effects through modulating ion channels via Gβγ subunits. Some of their side effects are attributed to β-arrestin recruitment, and several biased agonists that do not activate this pathway have been developed recently. Here we tested the effects of TRV130, PZM21 and herkinorin, three G-protein biased agonists of μ-opioid receptors (μOR), on ion channel targets. Compared to the full μOR agonist DAMGO, all three biased agonists induced smaller activation of G protein-coupled inwardly rectifying potassium channels (GIRK2), and smaller inhibition of Transient Receptor Potential Melastatin (TRPM3) channels. Furthermore, co-application of TRV130 or PZM21, but not herkinorin reduced the effects of DAMGO on both ion channels. CaV2.2 was also inhibited less by PZM21 and TRV130 than by DAMGO. TRV130, PZM21 and herkinorin were also less effective than DAMGO in inducing dissociation of the Gαi /Gβγ complex. We conclude that TRV130, PZM21 are partial agonists of μOR.

scholarly journals Different Activity Patterns in Retinal Ganglion Cells of TRPM1 and mGluR6 Knockout Mice

2018 ◽  
Vol 2018 ◽  
pp. 1-6 ◽  
Author(s):  
Haruki Takeuchi ◽  
Sho Horie ◽  
Satoru Moritoh ◽  
Hiroki Matsushima ◽  
Tesshu Hori ◽  
...  
Keyword(s):  
Retinal Ganglion Cells ◽  
Transient Receptor Potential ◽  
Metabotropic Glutamate Receptor ◽  
Ganglion Cells ◽  
Receptor Potential ◽  
Amacrine Cells ◽  
Bipolar Cells ◽  
Retinal Ganglion ◽  
Essential Components ◽  
Spontaneous Oscillations

TRPM1, the first member of the melanoma-related transient receptor potential (TRPM) subfamily, is the visual transduction channel downstream of metabotropic glutamate receptor 6 (mGluR6) on retinal ON bipolar cells (BCs). Human TRPM1 mutations are associated with congenital stationary night blindness (CSNB). In both TRPM1 and mGluR6 KO mouse retinas, OFF but not ON BCs respond to light stimulation. Here we report an unexpected difference between TRPM1 knockout (KO) and mGluR6 KO mouse retinas. We used a multielectrode array (MEA) to record spiking in retinal ganglion cells (RGCs). We found spontaneous oscillations in TRPM1 KO retinas, but not in mGluR6 KO retinas. We performed a structural analysis on the synaptic terminals of rod ON BCs. Intriguingly, rod ON BC terminals were significantly smaller in TRPM1 KO retinas than in mGluR6 KO retinas. These data suggest that a deficiency of TRPM1, but not of mGluR6, in rod ON bipolar cells may affect synaptic terminal maturation. We speculate that impaired signaling between rod BCs and AII amacrine cells (ACs) leads to spontaneous oscillations. TRPM1 and mGluR6 are both essential components in the signaling pathway from photoreceptors to ON BC dendrites, yet they differ in their effects on the BC terminal and postsynaptic circuitry.

scholarly journals The Human Transient Receptor Potential Melastatin 2 Ion Channel Modulates ROS Through Nrf2

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Lei Bao ◽  
Fernanda Festa ◽  
Christopher S. Freet ◽  
John P. Lee ◽  
Iwona M. Hirschler-Laszkiewicz ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Cell Viability ◽  
Transient Receptor Potential ◽  
Oxidant Stress ◽  
Receptor Potential ◽  
Related Factor ◽  
Wild Type ◽  
Transient Receptor Potential Melastatin ◽  
Transient Receptor ◽  
Nadh Generation

Abstract Transient receptor potential melastatin channel subfamily member 2 (TRPM2) has an essential role in protecting cell viability through modulation of oxidative stress. TRPM2 is highly expressed in cancer. When TRPM2 is inhibited, mitochondria are dysfunctional, ROS levels are increased, and cell viability is reduced. Here, the importance of NF-E2-related factor (Nrf2) in TRPM2-mediated suppression of oxidant stress was explored. In TRPM2 depleted cells, antioxidant cofactors glutathione, NADPH, and NADH were significantly reduced. Cytoplasmic and nuclear expression of Nrf2 and of IQGAP1, a modulator of Nrf2 stability regulated by intracellular calcium, were decreased. Antioxidant enzymes transcriptionally regulated by Nrf2 and involved in GSH, NADPH, and NADH generation were significantly lower including PRX1 and PRX3, GPX4, GSTP1, GCLC, and MTHFD2. The glutamine pathway leading to GSH production was suppressed, and ATP and GTP levels were impaired. Reconstitution with wild type TRPM2 or Nrf2, but not TRPM2 pore mutant E960D, rescued expression of enzymes downstream of Nrf2 and restored GSH and GTP. Cell viability, ROS, NADPH, NADH, and ATP levels were fully rescued by TRPM2 and partially by Nrf2. These data show that TRPM2 maintains cell survival following oxidative stress through modulation of antioxidant pathways and cofactors regulated by Nrf2.

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