scholarly journals TRPM8 acute desensitization is mediated by calmodulin and requires PIP2: distinction from tachyphylaxis

2011 ◽  
Vol 106 (6) ◽  
pp. 3056-3066 ◽  
Author(s):  
Ignacio Sarria ◽  
Jennifer Ling ◽  
Michael X. Zhu ◽  
Jianguo G. Gu
Keyword(s):  
Transient Receptor Potential ◽  
Channel Gating ◽  
Somatosensory System ◽  
Receptor Potential ◽  
Dorsal Root Ganglion Neurons ◽  
Open Probability ◽  
Cold Environments ◽  
Transient Receptor Potential Melastatin ◽  
Transient Receptor ◽  
Ganglion Neurons

The cold-sensing channel transient receptor potential melastatin 8 (TRPM8) features Ca2+-dependent downregulation, a cellular process underlying somatosensory accommodation in cold environments. The Ca2+-dependent functional downregulation of TRPM8 is manifested with two distinctive phases, acute desensitization and tachyphylaxis. Here we show in rat dorsal root ganglion neurons that TRPM8 acute desensitization critically depends on phosphatidylinositol 4,5-bisphosphate (PIP2) availability rather than PIP2 hydrolysis and is triggered by calmodulin activation. Tachyphylaxis, on the other hand, is mediated by phospholipase hydrolysis of PIP2 and protein kinase C/phosphatase 1,2A. We further demonstrate that PIP2 switches TRPM8 channel gating to a high-open probability state with short closed times. Ca2+-calmodulin reverses the effect of PIP2, switching channel gating to a low-open probability state with long closed times. Thus, through gating modulation, Ca2+-calmodulin provides a mechanism to rapidly regulate TRPM8 functions in the somatosensory system.

scholarly journals The proposed channel-enzyme transient receptor potential melastatin 2 does not possess ADP ribose hydrolase activity

eLife ◽  
2016 ◽  
Vol 5 ◽  
Author(s):  
Iordan Iordanov ◽  
Csaba Mihályi ◽  
Balázs Tóth ◽  
László Csanády
Keyword(s):  
Cell Death ◽  
Insulin Secretion ◽  
Transient Receptor Potential ◽  
Channel Gating ◽  
Receptor Potential ◽  
Cation Channel ◽  
Chimeric Proteins ◽  
Transient Receptor Potential Melastatin ◽  
Biochemical Studies ◽  
Transient Receptor

Transient Receptor Potential Melastatin 2 (TRPM2) is a Ca2+-permeable cation channel essential for immunocyte activation, insulin secretion, and postischemic cell death. TRPM2 is activated by ADP ribose (ADPR) binding to its C-terminal cytosolic NUDT9-homology (NUDT9H) domain, homologous to the soluble mitochondrial ADPR pyrophosphatase (ADPRase) NUDT9. Reported ADPR hydrolysis classified TRPM2 as a channel-enzyme, but insolubility of isolated NUDT9H hampered further investigations. Here we developed a soluble NUDT9H model using chimeric proteins built from complementary polypeptide fragments of NUDT9H and NUDT9. When expressed in E.coli, chimeras containing up to ~90% NUDT9H sequence remained soluble and were affinity-purified. In ADPRase assays the conserved Nudix-box sequence of NUDT9 proved essential for activity (kcat~4-9s-1), that of NUDT9H did not support catalysis. Replacing NUDT9H in full-length TRPM2 with soluble chimeras retained ADPR-dependent channel gating (K1/2~1-5 μM), confirming functionality of chimeric domains. Thus, TRPM2 is not a 'chanzyme'. Chimeras provide convenient soluble NUDT9H models for structural/biochemical studies.

scholarly journals Activation characteristics of transient receptor potential ankyrin 1 and its role in nociception

2011 ◽  
Vol 301 (3) ◽  
pp. C587-C600 ◽  
Author(s):  
Manish Raisinghani ◽  
Linlin Zhong ◽  
Joseph A. Jeffry ◽  
Mahendra Bishnoi ◽  
Reddy M. Pabbidi ◽  
...  
Keyword(s):  
Protein Kinase ◽  
Transient Receptor Potential ◽  
Receptor Potential ◽  
Nerve Fibers ◽  
Dorsal Root Ganglion Neurons ◽  
Whole Cell ◽  
Induced Currents ◽  
Transient Receptor ◽  
Ganglion Neurons ◽  
Single Channel Currents

Transient receptor potential (TRP) ankyrin 1 (TRPA1) is a Ca2+-permeant, nonselective cationic channel. It is predominantly expressed in the C afferent sensory nerve fibers of trigeminal and dorsal root ganglion neurons and is highly coexpressed with the nociceptive ion channel transient receptor potential vanilloid 1 (TRPV1). Several physical and chemical stimuli have been shown to activate the channel. In this study, we have used electrophysiological techniques and behavioral models to characterize the properties of TRPA1. Whole cell TRPA1 currents induced by brief application of lower concentrations of N-methyl maleimide (NMM) or allyl isothiocyanate (AITC) can be reversed readily by washout, whereas continuous application of higher concentrations of NMM or AITC completely desensitized the currents. The deactivation and desensitization kinetics differed between NMM and AITC. TRPA1 current amplitude increased with repeated application of lower concentrations of AITC, whereas saturating concentrations of AITC induced tachyphylaxis, which was more pronounced in the presence of extracellular Ca2+. The outward rectification exhibited by native TRPA1-mediated whole cell and single-channel currents was minimal as compared with other TRP channels. TRPA1 currents were negatively modulated by protons and polyamines, both of which activate the heat-sensitive channel, TRPV1. Interestingly, neither protein kinase C nor protein kinase A activation sensitized AITC-induced currents, but each profoundly sensitized capsaicin-induced currents. Current-clamp experiments revealed that AITC produced a slow and sustained depolarization as compared with capsaicin. TRPA1 is also expressed at the central terminals of nociceptors at the caudal spinal trigeminal nucleus. Activation of TRPA1 in this area increases the frequency and amplitude of miniature excitatory or inhibitory postsynaptic currents. In behavioral studies, intraplantar and intrathecal administration of AITC induced more pronounced and prolonged changes in nociceptive behavior than those induced by capsaicin. In conclusion, the characteristics of TRPA1 we have delineated suggest that it might play a unique role in nociception.

A Cool Channel in Cold Transduction

Physiology ◽  
2011 ◽  
Vol 26 (4) ◽  
pp. 273-285 ◽  
Author(s):  
Ramón Latorre ◽  
Sebastián Brauchi ◽  
Rodolfo Madrid ◽  
Patricio Orio
Keyword(s):  
Membrane Trafficking ◽  
Transient Receptor Potential ◽  
Somatosensory System ◽  
Physiological Role ◽  
Receptor Potential ◽  
Molecular Entity ◽  
Cool Channel ◽  
Cold Temperatures ◽  
Transient Receptor Potential Melastatin ◽  
Transient Receptor

Transient receptor potential melastatin 8 (TRPM8), a calcium-permeable cation channel activated by cold, cooling compounds and voltage, is the main molecular entity responsible for detection of cold temperatures in the somatosensory system. Here, we review the biophysical properties, physiological role, and near-membrane trafficking of this exciting polymodal ion channel.

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