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At least 19 recordsLinked to original sources
PubMed1997

Thermosensing properties of mutant aspartate chemoreceptors with methyl-accepting sites replaced singly or multiply by alanine.

The aspartate chemoreceptor Tar has a thermosensing function that is modulated by covalent modification of its four methylation sites (Gln295, Glu302, Gln309, and Glu491). Without posttranslational deamidation, Tar has no thermosensing ability. When Gln295 and Gln309 are deamidated to Glu, the unmethylated and heavily methylated forms function as warm and cold sensors, respectively. In this study, we carried out alanine-scanning mutagenesis of the methylation sites. Although alanine substitutions influenced the signaling bias and the methylation level, all of the mutants retained aspartate-sensing function. Those with single substitutions had almost normal thermosensing properties, indicating that substitutions at any particular methylation site do not seriously impair thermosensing function. In the posttranslational modification-defective background, some of the alanine substitutions restored thermosensing ability. Warm sensors were found among mutants retaining two glutamate residues, and cold sensors were found among those with one or no glutamate residue. This result suggests that the negative charge at the methylation sites is one factor that determines thermosensor phenotypes, although the size and shape of the side chain may also be important. The warm, cold, and null thermosensor phenotypes were clearly differentiated, and no intermediate phenotypes were found. Thus, the different thermosensing phenotypes that result from covalent modification of the methylation sites may reflect distinct structural states. Broader implications for the thermosensing mechanism are also discussed.

Alanine↗
PubMed1999

Inversion of thermosensing property of the bacterial receptor Tar by mutations in the second transmembrane region.

The aspartate chemoreceptor Tar of Escherichia coli serves as a warm sensor that produces attractant and repellent signals upon increases and decreases in temperature, respectively. However, increased levels of methylation of the cytoplasmic domain of Tar resulting from aspartate binding convert Tar to a cold sensor with the opposite signaling behavior. Detailed analyses of the methylation sites, which are located in two separate alpha-helices (MH1 and MH2), have suggested that intra- and/or intersubunit interactions of MH1 and MH2 play a critical role in thermosensing. These interactions may be influenced by binding of aspartate, which could trigger some displacement of MH1 through the second transmembrane region (TM2). As an initial step toward understanding the role of TM2 in thermosensing, we have examined the thermosensing properties of 43 mutant Tar receptors with randomized TM2 sequences (residues 190-210). Among them, we identified one mutant receptor (Tar-I2) that functioned as a cold sensor in the absence of aspartate. This is the first example of attractant-independent inversion of thermosensing in Tar. Further analyses identified the minimal essential divergence from the wild-type Tar sequence (Q191V-W192R-Q193C) required for the inverted response. Thus, displacements of TM2 seem to influence the thermosensing function of Tar.

Amino Acid Sequence↗
PubMed2006

Transient receptor potential ion channels as participants in thermosensation and thermoregulation.

Living organisms must evaluate changes in environmental and internal temperatures to mount appropriate physiological and behavioral responses conducive to survival. Classical physiology has provided a wealth of information regarding the specialization of thermosensory functions among subclasses of peripheral sensory neurons and intrinsically thermosensitive neurons within the hypothalamus. However, until recently, the molecular mechanisms by which these cells carry out thermometry have remained poorly understood. The demonstration that certain ion channels of the transient receptor potential (TRP) family can be activated by increases or decreases in ambient temperature, along with the recognition of their heterogeneous expression patterns and heterogeneous temperature sensitivities, has led investigators to evaluate these proteins as candidate endogenous thermosensors. Much of this work has involved one specific channel, TRP vanilloid 1 (TRPV1), which is both a receptor for capsaicin and related pungent vanilloid compounds and a "heat receptor," capable of directly depolarizing neurons in response to temperatures >42 degrees C. Evidence for a contribution of TRPV1 to peripheral thermosensation has come from pharmacological, physiological, and genetic approaches. In contrast, although capsaicin-sensitive mechanisms clearly influence core body temperature regulation, the specific contribution of TRPV1 to this process remains a matter of debate. Besides TRPV1, at least six additional thermally sensitive TRP channels have been identified in mammals, and many of these also appear to participate in thermosensation. Moreover, the identification of invertebrate TRP channels, whose genetic ablation alters thermally driven behaviors, makes it clear that thermosensation represents an evolutionarily conserved role of this ion channel family.

Animals↗
PubMed1996

Behavioral genetics of thermosensation and hygrosensation in Drosophila.

Whereas temperature and humidity are critical variables affecting physiology, behavior, and evolution, the genetic and neuronal underpinnings of thermosensation and hygrosensation remain poorly understood. We have initiated a behavioral-genetic investigation of these sensory systems in Drosophila. Behavioral tests are described for the rapid screening of mutants defective in thermosensation and hygrosensation. We demonstrate the strong responses of normal flies to temperature and humidity. Two mutants were found with defects in thermosensation, only one of which is also defective in hygrosensation, indicating that they involve different sensory mechanisms. Ablation experiments further separate these sensory systems by showing that thermoreceptors are housed in the third antennal segment, whereas hygroreceptors are located more distally in the antennal arista.

Animals↗
PubMed2005

Impaired thermosensation in mice lacking TRPV3, a heat and camphor sensor in the skin.

Environmental temperature is thought to be directly sensed by neurons through their projections in the skin. A subset of the mammalian transient receptor potential (TRP) family of ion channels has been implicated in this process. These "thermoTRPs" are activated at distinct temperature thresholds and are typically expressed in sensory neurons. TRPV3 is activated by heat (>33 degrees C) and, unlike most thermoTRPs, is expressed in mouse keratinocytes. We found that TRPV3 null mice have strong deficits in responses to innocuous and noxious heat but not in other sensory modalities; hence, TRPV3 has a specific role in thermosensation. The natural compound camphor, which modulates sensations of warmth in humans, proved to be a specific activator of TRPV3. Camphor activated cultured primary keratinocytes but not sensory neurons, and this activity was abolished in TRPV3 null mice. Therefore, heat-activated receptors in keratinocytes are important for mammalian thermosensation.

Animals↗
PubMed2004

[Molecular mechanisms of thermosensation].

We feel a wide range of temperatures spanning from cold to heat. Within this range, temperatures over about 43 degrees C and below about 15 degrees C evoke not only a thermal sensation, but also a feeling of pain. In mammals, six thermosensitive ion channels have been reported, all of which belong to the TRP (transient receptor potential) super family. These include TRPV1 (VR1), TRPV2 (VRL-1), TRPV3, TRPV4, TRPM8 (CMR1), and TRPA1 (ANKTM1). These channels exhibit distinct thermal activation thresholds (>43 degrees C for TRPV1, >52 degrees C for TRPV2, >32-39 degrees C for TRPV3, >27-35 degrees C for TRPV4, <25-28 degrees C for TRPM8, and <17 degrees C for TRPA1) and are expressed in primary sensory neurons as well as other tissues. The involvement of TRPV1 in thermal nociception has been demonstrated by multiple methods, including the analysis of TRPV1-deficient mice. Temperature thresholds for activation of TRPV1, TRPV4, and TRPM8 are not fixed but changeable. Reduction of the temperature threshold for TRPV1 activation is thought to be one mechanism of inflammatory pain. Significant advances in thermosensation research have been made in the last several years with the cloning and characterization of thermosensitive TRP channels. With these clones in hand, we can begin to understand thermosensation from a molecular standpoint.

Animals↗
PubMed1996

Modulation of the thermosensing profile of the Escherichia coli aspartate receptor tar by covalent modification of its methyl-accepting sites.

The Escherichia coli aspartate receptor Tar is involved in the thermotactic response. We have studied how its thermosensing function is affected by the modification of the four methyl-accepting residues (Gln295, Glu302, Gln309, and Glu491), which play essential roles in adaptation. We found that the primary translational product of tar mediates a chemoresponse, but not a thermoresponse, and that Tar comes to function as a thermoreceptor, once Gln295 or Gln309 is deamidated. This is the first identification of a thermosensing-specific mutant form, suggesting that the methylation sites of Tar constitute at least a part of the region required for thermoreception, signaling, or both. We have also investigated the inverted thermoresponse mediated by Tar in the presence of aspartate. We found that, whereas the deamidated-and-unmethylated form functions as a warm receptor, eliciting a smooth-swimming signal upon increase of temperature, the heavily methylated form functions as a cold receptor, eliciting a smooth-swimming signal upon decrease of temperature. Thus, it is suggested that Tar exists in at least three distinct states, each of which allows it to function as a warm, cold, or null thermoreceptor, depending on the modification patterns of its methylation sites.

Bacterial Proteins↗
PubMed2006

Individual differences in oral thermosensation.

Although oral thermosensation is critical to the perception of food and drinks, little information is available on the organization of individual differences in these abilities. We examined the relationship between measures of cooling and warming on the tongue and lip and the association of these measures to taste sensitivity in a sample of 76 healthy subjects. Thermal abilities were assessed with a computer-controlled, 1.5 cm2 peltier plate that was placed on the anterior dorsal surface of the tongue or the lower lip. Thermal testing consisted of both cooling and warming threshold detection, and intensity ratings of warm and cool suprathreshold temperatures. Intensity ratings of different temperatures were highly correlated, especially for temperatures in the same class. Similarly, warming and cooling thresholds were highly correlated. In contrast, thermal detection abilities were largely dissociable from suprathreshold intensity ratings, especially in the cooling direction. Suprathreshold ratings of cooling on the tongue were also modestly associated with ratings of the taste intensity of 6-n-propylthiouracil (PROP). However, a similar association was observed for the lower lip, indicating that the effect does not reflect an isolated characteristic of lingual physiology. Unexpectedly, two subjects with no history of oral trauma demonstrated abnormally deficient (4 S.D. below the mean) cool threshold detection abilities for the tongue, suggesting that there may exist subjects in the population who have profoundly poor lingual temperature processing.

Adult↗
PubMed2003

Thermosensation: hot findings make TRPNs very cool.

TRPV and TRPM proteins have been shown to form temperature-responsive cation channels that act in nociception. Recent work on the mouse ANKTM1 and Drosophila Painless proteins shows that members of a third TRP subfamily, TRPN, also function in thermosensation.

Animals↗
PubMed1996

Mutations in a cyclic nucleotide-gated channel lead to abnormal thermosensation and chemosensation in C. elegans.

The C. elegans tax-4 mutants are abnormal in multiple sensory behaviors: they fail to respond to temperature or to water-soluble or volatile chemical attractants. We show that the predicted tax-4 gene product is highly homologous to vertebrate cyclic nucleotide-gated channels. Tax-4 protein expressed in cultured cells functions as a cyclic nucleotide-gated channel. The green fluorescent protein (GFP)-tagged functional Tax-4 protein is expressed in thermosensory, gustatory, and olfactory neurons mediating all the sensory behaviors affected by the tax-4 mutations. The Tax-4::GFP fusion is partly localized at the sensory endings of these neurons. The results suggest that a cyclic nucleotide-gated channel is required for thermosensation and chemosensation and that cGMP is an important intracellular messenger in C. elegans sensory transduction.

Amino Acid Sequence↗
PubMed2003

Lessons from peppers and peppermint: the molecular logic of thermosensation.

Sensory neurons report a wide range of temperatures, from noxious heat to noxious cold. Natural products that elicit psychophysical sensations of hot or cold, such as capsaicin or menthol, were instrumental in the discovery of thermal detectors belonging to the transient receptor potential (TRP) family of cation channels. Studies are now beginning to reveal how these channels contribute to thermosensation and how chemical signaling pathways, such as those activated by tissue injury, alter thermal sensitivity through TRP channel modulation. Analysis of TRP channel expression among sensory neurons is also providing insight into how thermal stimuli are encoded by the peripheral nervous system.

Animals↗
PubMed1997

Thermoreceptors: recent heat in thermosensation.

Every organism with a nervous system can detect changes in temperature. Recent studies on sensory neurons from rats and genetic evidence from nematodes have provided intriguing hints about the molecular basis of thermosensation.

Animals↗
PubMed2001

Molecular basis of thermosensing: a two-component signal transduction thermometer in Bacillus subtilis.

Both prokaryotes and eukaryotes respond to a decrease in temperature with the expression of a specific subset of proteins. Although a large body of information concerning cold shock-induced genes has been gathered, studies on temperature regulation have not clearly identified the key regulatory factor(s) responsible for thermosensing and signal transduction at low temperatures. Here we identified a two-component signal transduction system composed of a sensor kinase, DesK, and a response regulator, DesR, responsible for cold induction of the des gene coding for the Delta5-lipid desaturase from Bacillus subtilis. We found that DesR binds to a DNA sequence extending from position -28 to -77 relative to the start site of the temperature-regulated des gene. We show further that unsaturated fatty acids (UFAs), the products of the Delta5-desaturase, act as negative signalling molecules of des transcription. Thus, a regulatory loop composed of the DesK-DesR two-component signal transduction system and UFAs provides a novel mechanism for the control of gene expression at low temperatures.

Artificial Gene Fusion↗
PubMed1988

Thermosensing properties of Escherichia coli tsr mutants defective in serine chemoreception.

Tsr, a chemoreceptor for serine and repellents in Escherichia coli, also functions as a thermoreceptor. The relationship between the chemoreceptor and thermoreceptor functions of Tsr was examined in five tsr mutants with altered serine detection thresholds. The thermosensing abilities of the mutant Tsr proteins were not affected by the alterations in their affinities to serine. In contrast, the ability of serine to inactivate thermoreceptor function was altered in these mutants. The minimal serine concentration required for thermoreceptor inactivation was directly related to the decreased affinity of the mutant Tsr for serine. The amino acid replacements in the mutant receptors were deduced from DNA sequence analyses and occurred at two different locations in the presumed periplasmic domain of Tsr. Two mutations caused histidine or cysteine replacements at arginine 64, whereas three others caused isoleucine or proline replacements at threonine 156.

Amino Acid Sequence↗
PubMed1991

Thermosensing ability of Trg and Tap chemoreceptors in Escherichia coli.

The thermosensing ability of the Trg and Tap chemoreceptors in Escherichia coli was investigated after amplifying these receptors in a host strain lacking all four known chemoreceptors (Tar, Tsr, Trg, and Tap). Cells with an increased amount of either Trg or Tap showed mostly smooth swimming and no response to thermal stimuli. However, when the smooth-swimming bias of the cells was reduced by adding Trg- or Tap-mediated repellents, the cells showed clear changes in the swimming pattern upon temperature changes; Trg-containing cells showed tumbling at 23 degrees C but mostly smooth swimming at 32 degrees C, while Tap-containing cells showed smooth swimming at 20 degrees C but tumbling at 32 degrees C. These results indicate that although both Trg and Tap have the ability to sense thermal stimuli, Trg functions as a warm receptor, as reported previously for Tar and Tsr, while Tap functions as a cold receptor.

Bacterial Proteins↗
PubMed2006

A hot-sensing cold receptor: C-terminal domain determines thermosensation in transient receptor potential channels.

Temperature transduction in mammals is possible because of the presence of a set of temperature-dependent transient receptor potential (TRP) channels in dorsal root ganglia neurons and skin cells. Six thermo-TRP channels, all characterized by their unusually high temperature sensitivity (Q10 > 10), have been cloned: TRPV1-4 are heat activated, whereas TRPM8 and TRPA1 are activated by cold. Because of the lack of structural information, the molecular basis for regulation by temperature remains unknown. In this study, we assessed the role of the C-terminal domain of thermo-TRPs and its involvement in thermal activation by using chimeras between the heat receptor TRPV1 and the cold receptor TRPM8, in which the entire C-terminal domain was switched. Here, we demonstrate that the C-terminal domain is modular and confers the channel phenotype regarding temperature sensitivity, channel gating kinetics, and PIP2 (phosphatidylinositol-4,5-bisphophate) modulation. Thus, thermo-TRP channels contain an interchangeable specific region, different from the voltage sensor, which allows them to sense temperature stimuli.

Analysis of Variance↗