Sweet tastants stimulate adenylate cyclase coupled to GTP-binding protein in rat tongue membranes

Striem, Benjamin J.; Pace, Umberto; Zehavi, Uri; Naim, Michael; Lancet, Doron

doi:10.1042/bj2600121

Cited by 161 publications

(79 citation statements)

References 39 publications

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“…A member of the mammalian Gα subfamily, Gs, stimulates adenylyl cyclase, thus elevating cAMP concentrations [78,79]. This cAMP signal transduction pathway has been shown to be involved in sugar perception [84][85][86]. Additionally, the Gα subunit of the taste receptor-specific G-protein gustducin is required for mammalian behavioral response to bitter and sweet compounds [87].…”

Section: Signal Transductionmentioning

confidence: 99%

Taste and pheromone perception in the fruit fly Drosophila melanogaster

Ebbs

Amrein

2007

Pflugers Arch - Eur J Physiol

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Taste is an essential sense for detection of nutrient-rich food and avoidance of toxic substances. The Drosophila melanogaster gustatory system provides an excellent model to study taste perception and taste-elicited behaviors. "The fly" is unique in the animal kingdom with regard to available experimental tools, which include a wide repertoire of molecular-genetic analyses (i.e., efficient production of transgenics and gene knockouts), elegant behavioral assays, and the possibility to conduct electrophysiological investigations. In addition, fruit flies, like humans, recognize sugars as a food source, but avoid bitter tasting substances that are often toxic to insects and mammals alike. This paper will present recent research progress in the field of taste and contact pheromone perception in the fruit fly. First, we shall describe the anatomical properties of the Drosophila gustatory system and survey the family of taste receptors to provide an appropriate background. We shall then review taste and pheromone perception mainly from a molecular genetic perspective that includes behavioral, electrophysiological and imaging analyses of wild type flies and flies with genetically manipulated taste cells. Finally, we shall provide an outlook of taste research in this elegant model system for the next few years.Keywords Drosophila . Gustatory receptor neurons . GTP-binding protein-coupled receptors Like most animals, Drosophila monitor their chemical world with two distinct senses: the olfactory system, which is used for the detection of volatile chemicals, and the gustatory (taste) system, which enables the fly to detect soluble compounds. The olfactory sensory system (or the fly nose) is comprised of two pairwise head appendages, the third segments of the antennae, and the maxillary palps (Fig. 1). These appendages are covered with hundreds of sensory hairs, each of which contains two to four olfactory sensory neurons (OSNs) [1]. In contrast, the gustatory system is widely distributed over the animal's body. The main taste organ, the proboscis or labial palps (i.e., the fly tongue), is located on the distal end of the labellum (also a head appendage), but flies, like many other insects, have taste sensilla on legs and wings and, in females, on the genitalia [1,2].The roles of the olfactory and taste systems are clearly separated with regard to the physical state of chemicals they detect (volatile vs solubilized). However, the two systems often cooperate to fulfill specific functions in related processes and behaviors, the most obvious of them being the location and identification of food. For example, chemical cues such as the specific odor of a flower and the sugar compounds present in its nectar are by nature associated with one another. Thus, the odor cue provides a primary sensory input for an insect such as a honeybee to locate a food source (nectar), whose particular chemical composition is subsequently verified by the taste system. Similarly, the typical odor of yeast, which produces high amounts of t...

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Section: Signal Transductionmentioning

confidence: 99%

Taste and pheromone perception in the fruit fly Drosophila melanogaster

Ebbs

Amrein

2007

Pflugers Arch - Eur J Physiol

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“…For the rat, an adenylate cyclase stimulated by sweet agents was reported (Striem et al, 1989), and intact taste cells were recently shown to generate cAMP in response to exposure with sucrose (Striem et al, 1990). In the frog, cAMP caused an inhibition of outward current and a depolarization in ~50% of the TRCs investigated (Avenet and Lindemann, 1987b).…”

Section: Response To Sweetmentioning

confidence: 99%

Membrane currents in taste cells of the rat fungiform papilla. Evidence for two types of Ca currents and inhibition of K currents by saccharin.

Béhé

DeSimone

Avenet

et al. 1990

The Journal of General Physiology

171

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Taste buds were isolated from the fungiform papilla of the rat tongue and the receptor cells (TRCs) were patch clamped. Seals were obtained on the basolateral membrane of 281 TRCs, protruding from the intact taste buds or isolated by micro-dissection. In whole-cell configuration 72% of the cells had a TTX blockable transient Na inward current (mean peak amplitude 0.74 hA). All cells had outward K currents. Their activation was slower than for the Na current and a slow inactivation was also noticeable. The K currents were blocked by tetraethylammonium, Ba, and 4-aminopyridine, and were absent when the pipette contained Cs instead of K. With 100 mM Ba or 100 mM Ca in the bath, two types of inward current were observed. An L-type Ca current (ICaL) activated at -20 mV had a mean peak amplitude of 440 pA and inactivated very slowly. At 3 mM Ca the activation threshold of ICa L was near -40 mV. A transient T-type current (/CAT) activated at -50 mV had an average peak amplitude of 53 pA and inactivated with a time constant of 36 ms at -30 inV. ICR L was blocked more efficiently by Cd and D600 than/Ca T. ICa T was blocked by 0.2 mM Ni and half blocked by 200 #M amiloride. In whole-cell voltage clamp, Na-saccharin caused (in 34% of 55 cells tested) a decrease in outward K currents by 21%, which may be expected to depolarize the TRCs. Also, Na-saccharin caused some taste cells to fire action potentials (on-ceLl, 7 out of 24 cells; whole-ceLl, 2 out of 38 cells responding to saccharin) of amplitudes sufficient to activate/CAL. ThUS the action potentials will cause Ca inflow, which may trigger release of transmitter.

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“…The earliest identified tastetransduction stream involved the second messenger cyclic adenosine monophosphate (cAMP). Decades ago, Striem et al [101] reported that treating membranes derived from the anterior surface of rat tongues with sucrose stimulated adenylyl cyclase, implying the presence of G as proteins and Focussed search with primers based on synaptic glutamate receptors cAMP pathways in taste. These studies have been replicated and extended, using intact taste tissue [102].…”

Section: Second-messenger Cascades and Taste Gpcrsmentioning

confidence: 99%

Signal transduction and information processing in mammalian taste buds

Roper

2007

Pflugers Arch - Eur J Physiol

271

215

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The molecular machinery for chemosensory transduction in taste buds has received considerable attention within the last decade. Consequently, we now know a great deal about sweet, bitter, and umami taste mechanisms and are gaining ground rapidly on salty and sour transduction. Sweet, bitter, and umami tastes are transduced by G-protein-coupled receptors. Salty taste may be transduced by epithelial Na channels similar to those found in renal tissues. Sour transduction appears to be initiated by intracellular acidification acting on acidsensitive membrane proteins. Once a taste signal is generated in a taste cell, the subsequent steps involve secretion of neurotransmitters, including ATP and serotonin. It is now recognized that the cells responding to sweet, bitter, and umami taste stimuli do not possess synapses and instead secrete the neurotransmitter ATP via a novel mechanism not involving conventional vesicular exocytosis. ATP is believed to excite primary sensory afferent fibers that convey gustatory signals to the brain. In contrast, taste cells that do have synapses release serotonin in response to gustatory stimulation. The postsynaptic targets of serotonin have not yet been identified. Finally, ATP secreted from receptor cells also acts on neighboring taste cells to stimulate their release of serotonin. This suggests that there is important information processing and signal coding taking place in the mammalian taste bud after gustatory stimulation.

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Sweet tastants stimulate adenylate cyclase coupled to GTP-binding protein in rat tongue membranes

Cited by 161 publications

References 39 publications

Taste and pheromone perception in the fruit fly Drosophila melanogaster

Taste and pheromone perception in the fruit fly Drosophila melanogaster

Membrane currents in taste cells of the rat fungiform papilla. Evidence for two types of Ca currents and inhibition of K currents by saccharin.

Signal transduction and information processing in mammalian taste buds

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