Uncommon opsin's retinal isomer is involved in mammalian sperm thermotaxis

In recent years it became apparent that, in mammals, rhodopsin and other opsins, known to act as photosensors in the visual system, are also present in spermatozoa, where they function as highly sensitive thermosensors for thermotaxis. The intriguing question how a well-conserved protein functions as a photosensor in one type of cells and as a thermosensor in another type of cells is unresolved. Since the moiety that confers photosensitivity on opsins is the chromophore retinal, we examined whether retinal is substituted in spermatozoa with a thermosensitive molecule. We found by both functional assays and mass spectrometry that retinal is present in spermatozoa and required for thermotaxis. Thus, starvation of mice for vitamin A (a precursor of retinal) resulted in loss of sperm thermotaxis, without affecting motility and the physiological state of the spermatozoa. Thermotaxis was restored after replenishment of vitamin A. Using reversed-phase ultra-performance liquid chromatography mass spectrometry, we detected the presence of retinal in extracts of mouse and human spermatozoa. By employing UltraPerformance convergence chromatography, we identified a unique retinal isomer in the sperm extracts-tri-cis retinal, different from the photosensitive 11-cis isomer in the visual system. The facts (a) that opsins are thermosensors for sperm thermotaxis, (b) that retinal is essential for thermotaxis, and (c) that tri-cis retinal isomer uniquely resides in spermatozoa and is relatively thermally unstable, suggest that tri-cis retinal is involved in the thermosensing activity of spermatozoa.

Light and temperature perceptions go through a phase separation

Light and temperature are two distinct but closely linked environmental factors that profoundly affect plant growth and development. Biomolecular condensates are membraneless micron-scale compartments formed through liquid-liquid phase separation, which have been shown to be involved in a wide range of biological processes. In the last few years, biomolecular condensates are emerged to serve as phase separation-based sensors for plant sensing and/or responding to external environmental cues. This review summarizes the recently reported plant biomolecular condensates in sensing light and temperature signals. The current understanding of the biophysical properties and the action modes of phase separation-based environmental sensors are highlighted. Unresolved questions and possible challenges for future studies of phase-separation sensors are also discussed.

Temperature Matters: Bacterial Response to Temperature Change

Temperature is one of the most important factors in all living organisms for survival. Being a unicellular organism, bacterium requires sensitive sensing and defense mechanisms to tolerate changes in temperature. During a temperature shift, the structure and composition of various cellular molecules including nucleic acids, proteins, and membranes are affected. In addition, numerous genes are induced during heat or cold shocks to overcome the cellular stresses, which are known as heat- and cold-shock proteins. In this review, we describe the cellular phenomena that occur with temperature change and bacterial responses from a molecular perspective, mainly in Escherichia coli.

Temperature Sensing in Plants: On the Dawn of Molecular Thermosensor Research

Although many studies on plant growth and development focus on the effects of light, a growing number of studies dissect plant responses to temperature and the underlying signaling pathways. The identity of plant thermosensing molecules (thermosensors) acting upstream of the signaling cascades in temperature responses was elusive until recently. During the past six years, a set of plant thermosensors has been discovered, representing a major turning point in the research on plant temperature responses and signaling. Here, we review these newly discovered plant thermosensors, which can be classified as sensors of warmth or cold. We compare between plant thermosensors and those from other organisms and attempt to define the subcellular thermosensing compartments in plants. In addition, we discuss the notion that photoreceptive thermosensors represent a novel class of thermosensors, the roles of which have yet to be described in non-plant systems.

Thermogenetics: Applications come of age

Temperature is a ubiquitous physical cue that is non-invasive, penetrative and easy to apply. In the growing field of thermogenetics, through beneficial repurposing of natural thermosensing mechanisms, synthetic biology is bringing new opportunities to design and build robust temperature-sensitive (TS) sensors which forms a thermogenetic toolbox of well characterised biological parts. Recent advancements in technological platforms available have expedited the discovery of novel or de novo thermosensors which are increasingly deployed in many practical temperature-dependent biomedical, industrial and biosafety applications. In all, the review aims to convey both the exhilarating recent technological developments underlying the advancement of thermosensors and the exciting opportunities the nascent thermogenetic field holds for biomedical and biotechnology applications.

Safety of Thermosensor Insertion in the Midline of the Spinal Canal Anterior to the Dura: A Cadaveric Study

OBJECTIVE

To evaluate the safety of the insertion of a blunt-tip thermosensor inside the anterior epidural space using the trans-osseous route in the dorsal spine and the double oblique trans-foraminal approach in the lumbar spine.

MATERIALS AND METHODS

A total of 10 attempts were made on a 91 years old human specimen. Thermosensors were inserted under fluoroscopic guidance in the anterior part of the spinal canal using various oblique angulations. Surgical dissection was then performed to identify the position of the thermosensor and look for any injury to the dural sac or the spinal cord/cauda equina.

RESULTS

Nine thermosensors could be deployed successfully in the anterior part of the spinal canal from Th8 to L5 while one attempt (L5 level) failed due to a technical issue on the coaxial needle. On anteroposterior projection, the tip of thermosensor relative to the midline was classified as centered in 5 cases, overcrossing in 3 cases and undercrossing in 1 case. At surgical dissection, the tip of the thermosensor was epidural posterior to the posterior longitudinal ligament in 8 cases and anterior to the longitudinal ligament in 1 case (the undercrossing case). There were 3 tears to the dura, all in the overcrossing group. There was no case of injury to the spinal cord/cauda equina.

CONCLUSION

Insertion of a thin blunt-tip thermosensor with optimal angulation leads to an epidural post-ligamentous position on the midline without damage to the dural sac. The blunt-tip did not prevent from dural tearing should the insertion overcross the midline.

The conundrum of hot mitochondria

The mitochondrion is often referred as the cellular powerhouse because the organelle oxidizes organic acids and NADH derived from nutriments, converting around 40% of the Gibbs free energy change of these reactions into ATP, the major energy currency of cell metabolism. Mitochondria are thus microscopic furnaces that inevitably release heat as a by-product of these reactions, and this contributes to body warming, especially in endotherms like birds and mammals. Over the last decade, the idea has emerged that mitochondria could be warmer than the cytosol, because of their intense energy metabolism. It has even been suggested that our own mitochondria could operate under normal conditions at a temperature close to 50 °C, something difficult to reconcile with the laws of thermal physics. Here, using our combined expertise in biology and physics, we exhaustively review the reports that led to the concept of a hot mitochondrion, which is essentially based on the development and use of a variety of molecular thermosensors whose intrinsic fluorescence is modified by temperature. Then, we discuss the physical concepts of heat diffusion, including mechanisms like phonons scattering, which occur in the nanoscale range. Although most of approaches with thermosensors studies present relatively sparse data and lack absolute temperature calibration, overall, they do support the hypothesis of hot mitochondria. However, there is no convincing physical explanation that would allow the organelle to maintain a higher temperature than its surroundings. We nevertheless proposed some research directions, mainly biological, that might help throw light on this intriguing conundrum.

Versatile Processing of Metal-Organic Framework-Fluoropolymer Composite Inks with Chemical Resistance and Sensor Applications

We report a new class of metal-organic framework (MOF) inks with a water-repellent, photocurable fluoropolymer (PFPE) having up to 90 wt % MOF loading. These MOF inks are enabled to process various MOFs through spray coating, pen writing, stencil printing, and molding at room temperature. Upon UV curing, the hydrophobic PFPE matrix efficiently blocks water permeation but allows accessibility of chemicals into the MOF pores, thereby freeing the MOF to perform its unique function. Moreover, by introducing functional MOFs we successfully demonstrated a water-tolerant chemosensor for a class of aromatic pollutants in water and a chemical-resistant thermosensor for visualizing temperature image. This approach would open up innumerable opportunities for those MOFs that are otherwise dormant.

TRPV4: a Sensor for Homeostasis and Pathological Events in the CNS

Transient receptor potential vanilloid type 4 (TRPV4) was originally described as a calcium-permeable nonselective cation channel. TRPV4 is now recognized as a polymodal ionotropic receptor: it is a broadly expressed, nonselective cation channel (permeable to calcium, potassium, magnesium, and sodium) that plays an important role in a multitude of physiological processes. TRPV4 is involved in maintaining homeostasis, serves as an osmosensor and thermosensor, can be activated directly by endogenous or exogenous chemical stimuli, and can be activated or sensitized indirectly via intracellular signaling pathways. Additionally, TRPV4 is upregulated in a variety of pathological conditions. In this review, we focus on the role of TRPV4 in mediating homeostasis and pathological events in the central nervous system (CNS). This review is composed of three parts. Section 1 describes the role of TRPV4 in maintaining homeostatic processes, including the volume of body water, ionic concentrations, volume, and the temperature. Section 2 describes the effects of activation and inhibition of TRPV4 in the CNS. Section 3 focuses on the role of TRPV4 during pathological events in CNS.

A simple and inexpensive thermal optic nanosensor formed by triblock copolymer and polydiacetylene mixture

Polydiacetylene (PDA) vesicles have been applied as optical sensors in different areas, although there are difficulties in controlling their responses. In this study, we prepared nanoblends of PDA with triblock copolymers (TC) as a better sensor system for detecting temperature change. The influences of diacetylene (DA) monomer, and the TC chemical structure and concentration on the colorimetric response (CR) were examined. The TC/PDA nanoblend was remarkably more sensitive to temperature change, than classical vesicles. A higher L64 concentration of 12.0% (w/w) reduced the chromatic transition temperature (T_tr) to as low as 24°C. When using different TCs, the T_tr values can be ordered as L35<F68<L64<F127<P123, indicating the importance of the hydrophobic environment for the colorimetric transition of nanoblends. The results here demonstrated that the balance of intermolecular interaction between TC-TC, TC-DA, and DA-DA enables the construction of strategic sensor for detecting temperature changes in different applications.

Physiological significance of TRPV2 as a mechanosensor, thermosensor and lipid sensor

This review provides a summary of the physiological significance of the TRPV2 ion channel. While TRPV2 was initially characterized as a noxious heat sensor, we found that TRPV2 can also act as a mechanosensor in embryonic neurons or adult myenteric neurons. Here, we summarize the newly characterized functions of TRPV2, including the research progress that has been made toward our understanding of TRPV2 physiology, and discuss other recent data pertaining to TRPV2. It is thought that TRPV2 may be an important drug target based on its broad expression patterns and important physiological roles. The possible associations between diseases and TRPV2 are also discussed.

TRPV4 ion channel as important cell sensors

This review provides a summary of the physiological significance of the TRPV4 ion channel. Although TRPV4 was initially characterized as an osmosensor, we found that TRPV4 can also act as a thermosensor or a mechanosensor in brain neurons or epithelial cells in the urinary bladder. Here, we summarize the newly characterized functions of TRPV4, including the research progress that has been made toward our understanding of TRPV4 physiology, and discuss other recent data pertaining to TRPV4. It is thought that TRPV4 may be an important drug target based on its broad expression patterns and important physiological functions. Possible associations between diseases and TRPV4 are also discussed.