In winter we blame the cold, in summer we curse the heat. Cold and heat, two perceptions, individual and opposing. But it is also the result of a complex mechanism of which a further detail is now known: the protein that allows mammals to sense the cold has been identified.
The authors of the discovery were researchers from the University of Michigan who, coordinated by the neuroscientist Shawn Xu, professor of the Sciences Institute, published the results on Nature Neuroscience. This could be the key to deciphering the mechanism by which we perceive the cold in winter and, also, to understanding the reason why some patients, in particular pathological conditions, feel it differently. The protein with the acronym GluK2 (Glutamate ionotropic receptor kainate type subunit 2) has already been renamed “cold sensor” because it allows us to perceive temperatures below 15 degrees.
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The experiment in the laboratory
“Temperature sensors were identified over 20 years ago – explains Shawn Xu – with the discovery of a heat-sensitive protein, Trpv1. Then, thanks to subsequent studies, proteins that detect hot, warm and even cold, but we were unable to confirm the one which detects temperatures below 60° Fahrenheit (15° centigrade)”.
The research involved a mouse model, but, the authors point out, even if mice respond normally to heat and stimuli, “they show a deficit in detecting cold but not very cold temperatures”.
In a worm many answers
The story starts from a 2019 study, when in Xu’s laboratory the first cold-sensing receptor protein was identified in a worm just one millimeter long, Caenorhabditis elegans, used as a model to understand sensory responses. GluK2 is found mainly on the neurons of the brain, from which the chemical signals suitable for communication between the neurons themselves arrive. Mainly but not only, given that the protein is also expressed in sensory neurons of the peripheral nervous system (i.e. outside the brain and spinal cord).
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“We thus understood that this protein – precise Bo Duanco-senior author of the study – serves a completely different function in the peripheral nervous system, processing temperature and non-chemical signals to sense cold.”
About GluK2, Xu speculates that temperature sensing may have been one of the protein’s original purposes: “The GluK2 gene has relatives along the evolutionary tree, all the way back to single-celled bacteria. But a bacterium has no brain, so why would it develop a way to receive chemical signals from other neurons? So I think temperature sensing may be an ancient function.”
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The effects of studies on cancer patients
One wonders what repercussions the discovery might have. And Xu immediately replies: “About health in general, but also about cancer patients undergoing chemo who often suffer painful reactions to the cold.”
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But how does thermoregulation occur at the hypothalamic level? He explains it Andrea Giustinadirector of the Institute of Endocrine and Metabolic Sciences of the Irccs San Raffaele in Milan: “The hypothalamus is that portion of the central nervous system in close contact (anatomical and functional) with the pituitary gland which in turn regulates many endocrine functions.
The anterior preoptic region of the hypothalamus is equipped with receptors for heat (“warm receptors”) and for cold (“cold receptors”). The well-studied “warms” belong to the family of adrenergic receptors activated by an increase in blood temperature.
Following this activation, a signal is transmitted to the hypothalamus which, in turn, induces bodily responses aimed at dissipating excess heat, such as vasodilation and sweating. On the contrary, the “cold receptors”, when activated, transmit their signal to the neurons of the medial region of the posterior hypothalamus which activate energy conservation mechanisms (vasoconstriction and increased heat production through tremor)”.
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The peripheral nervous system
Then, as well as at the level of the central nervous system, the receptors for hot and cold are also present in the sensory neurons of the peripheral nervous system, activated by the external environment. What’s new about the research? “GluK2 could help better understand and perhaps treat some spontaneous or drug-induced conditions of excessive cold sensitivity.”
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#cold #proteins #fault
– 2024-04-04 04:45:23
