Biology subjects

Viana, F.

Publications and source records attributed to Viana, F..

5 recordsLinked to original sources

bioRxiv2025

A specialized cold sensing system in the naked mole-rat

Avoiding cold or seeking warmth are universal animal needs. Homeothermic mammals maintain a constant body temperature despite fluctuating ambient temperatures. One exception is the naked mole-rat which lacks effective thermogenesis. We show that the naked mole-rat has evolved a greatly expanded cold sensing system. Compared to mice, this species has many more cold-sensitive sensory neurons and most express the cold-activated TRPM8 channel. The naked mole-rat TrpM8 gene harbors a unique upstream exon that when translated produces a TRPM8 protein with a 71 amino acid N-terminal extension. When expressed, the N-terminal extension prevents membrane targeting and abolishes TRPM8 function. Splice forms lacking the extension formed functional cold and menthol activated channels in vivo. Additionally, many naked mole-rat sensory neurons use a TRPM8-independent mechanism to detect cold. Thus, we identified molecular changes that confer both sensitivity and flexibility to cold sensing in a species that is critically dependent on following thermal cues.

neuroscience↗

bioRxiv2024

The ion channel TRPM8 is a direct target of the immunosuppressant rapamycin in primary sensory neurons

Background and PurposeThe mechanistic target of rapamycin (mTOR) signaling pathway is a key regulator of cell growth and metabolism. Its deregulation is implicated in several diseases. The macrolide rapamycin (RAP), a specific inhibitor of mTOR, has immunosuppressive, anti-inflammatory and antiproliferative properties. Recently, we identified tacrolimus, another macrolide immunosuppressant, as a novel activator of TRPM8 ion channels, involved in cold temperature sensing, thermoregulation, tearing and cold pain. We hypothesized that RAP may also have agonist activity on TRPM8. Experimental approachUsing calcium imaging and electrophysiology in transfected HEK293 cells and wildtype or Trpm8 KO mouse DRG neurons, we characterized RAP effects on TRPM8. We also examined the effects of RAP on tearing in mice. Key ResultsMicromolar concentrations of RAP activate rat and mouse TRPM8 directly and potentiate cold-evoked responses. These effects were also observed in human TRPM8. In cultured mouse DRG neurons, RAP evoked an increase in intracellular calcium almost exclusively in cold-sensitive neurons. Responses were drastically blunted in Trpm8 KO mice or by TRPM8 antagonists. Cutaneous cold thermoreceptor endings were also activated by RAP. Topical application of RAP to the eye surface evokes tearing in mice by a TRPM8-dependent mechanism. Conclusion and implicationsThese results identify TRPM8 cationic channels in sensory neurons as novel molecular targets of the immunosuppressant RAP. These findings may help explain some of its therapeutic effects after topical application to the skin and the eye surface. Moreover, RAP could be used as an experimental tool in the clinic to explore cold thermoreceptors. Bullet point summaryWHAT IS ALREADY KNOWN O_LITRPM8 is a polymodal channel involved in cold detection, thermoregulation, tearing and cold pain C_LIO_LITacrolimus, a macrolide immunosupressor, is an agonist of cold-activated TRPM8 channels C_LI WHAT THIS STUDY ADDS O_LIThe macrolide rapamycin also activates directly TRPM8 channels in mouse sensory neurons and human TRPM8 C_LIO_LIRapamycin stimulates tearing in mice in a TRPM8-dependent manner CLINICAL SIGNIFICANCE C_LIO_LIRapamycin, an FDA-approved drug, shows agonist activity on TRPM8 channels C_LIO_LIBeneficial effects of rapamycin and other macrolides on inflammatory ocular disorders may involve TRPM8 activation C_LI

neuroscience↗

bioRxiv2022

Validation of six commercial antibodies for detection of heterologous and endogenous TRPM8 ion channel expression

TRPM8 is a non-selective cation channel expressed in primary sensory neurons and other tissues, including prostate and urothelium. Its participation in different physiological and pathological processes such as thermoregulation, pain, itch, inflammation and cancer has been widely described, making it a promising target for therapeutic approaches. The detection and quantification of TRPM8 seems crucial for advancing in the knowledge of the mechanisms under-lying its role in these pathophysiological conditions. Antibody-based techniques are commonly used for protein detection and quantification, although their performance with many ion channels, including TRPM8, is suboptimal. Thus, the search for reliable antibodies is of utmost importance. In this study, we characterized the performance of six TRPM8 commercial antibodies in three immunodetection techniques: western blot, immunocytochemistry and immunohistochemistry. Different outcomes were obtained for the tested antibodies; two of them proved to be successful detecting TRPM8 in the three approaches while, in the conditions tested, the other four were acceptable only for specific techniques. Considering our results, we offer some insight into the usefulness of these antibodies for detection of TRMP8 depending on the methodology of choice.

neuroscience↗

bioRxiv2021

Zebrafish larvae as a powerful model to dissect protective innate immunity in response to Legionella pneumophila infection

The zebrafish has become a powerful model organism to study host-pathogen interactions. Here, we developed a zebrafish model of Legionella pneumophila infection to dissect innate immune responses. We show that L. pneumophila cause zebrafish larvae death in a dose dependent manner, and that macrophages are the first line of defence, with neutrophils cooperating to clear the infection. When either macrophages or neutrophils are depleted, these "immunocompromised" larvae become lethally sensitive to L. pneumophila similar to what is known for humans that develop pneumonia. Also as observed in human infections, the adaptor signalling molecule Myd88 is not required to control disease in the larvae. Furthermore, proinflammatory cytokine genes il1{beta} and tnf were upregulated during infection, recapitulating key immune responses seen in human infection. Strikingly, we uncovered a previously undescribed infection phenotype in zebrafish larvae, whereby bloodborne, wild type L. pneumophila invade and grow in the larval yolk region, a phenotype not observed with a type IV secretion system deficient mutant that cannot translocate effectors into its host cell. Thus, zebrafish larva represents an innovative L. pneumophila infection model that that on one hand mimics important aspects of the human immune response to L. pneumophila infection and that on the other hand will allow to elucidate the mechanisms by which type IV secretion effectors allow L. pneumophila to cross membranes and to obtain nutrients from nutrient rich environments.

microbiology↗

bioRxiv2021

Differential mechanisms of cold sensitivity in mouse trigeminal and vagal ganglion neurons

Thermal signals are critical elements in the operation of interoceptive and exteroceptive neural circuits, essential for triggering thermally-driven reflexes and conscious behaviors. A fraction of cutaneous and visceral sensory endings are activated by cold temperatures. Compared to somatic (DRG and TG) neurons, little is known about the mechanisms underlying cold sensitivity of visceral vagal neurons. We used molecular, pharmacological and genetic tools for a side-by-side characterization of cold-sensitive (CS) neurons in adult mouse trigeminal (TG) and vagal ganglia (VG). We found that CS neurons are larger in size and more abundant in VG than in TG. In VG, the majority of CS neurons co-express TRPA1 markers and cold-evoked responses are severely blunted in Trpa1 KO mice. Cold sensitivity was evident in neurons with the highest TRPA1 expression. In contrast, TRPM8 deletion or pharmacological TRPM8 blockade had little impact on VG cold sensitivity. Consistent with these findings, in Trpm8eYFP reporter mice we found limited expression of TRPM8 in VG and restricted to the rostral jugular ganglion. In vivo retrograde labelling of airway-innervating vagal neurons demonstrated their enhanced cold sensitivity and a higher expression of TRPA1 compared to neurons innervating the stomach wall. In contrast, the majority of CS TG neurons co-express TRPM8 markers and their cold sensitivity is reduced after TRPM8 deletion or blockade. However, pharmacological or genetic reduction of TRPA1 showed that these channels contribute significantly to high-threshold cold sensitivity in TG, suggestive of a role in noxious cold sensing. In both ganglia, a fraction of CS neurons responded to cooling by a mechanism independent of TRPA1 or TRPM8 yet to be characterized. Finally, in both ganglia, sensitivity to cold varied widely and was enhanced by the potassium channel blocker 4-AP. This effect was independent of the cold sensor expressed by the neuron, suggestive of a common excitability brake mechanism. Significance statementTemperature sensing and its regulation is a critical homeostatic function. Little is known about the molecular mechanism of cold sensing by visceral sensory endings and their relative weight in different visceral organs. This study highlights important differences in thermotransduction mechanisms between somatic (trigeminal) and visceral (vagal) primary sensory neurons, establishing a critical role of TRPA1 channels in visceral cold transduction. The study describes quantitative differences in cold sensitivity of visceral neurons innervating the stomach and the lower airways, suggesting that cold transduction mechanisms may be fine-tuned to the specific needs of different organs. This study significantly advances our understanding of cold sensing in trigeminal and vagal neurons and reveals distinct drug targets for the pharmacological modulation of these thermoreceptors.

neuroscience↗