Tomosyn Expression Pattern in the Mouse Hippocampus Suggests Both Presynaptic and Postsynaptic Functions

The protein tomosyn decreases synaptic transmission and release probability of vesicles, and is essential for modulating synaptic transmission in neurons. In this study, we provide a detailed description of the expression and localization patterns of tomosyn1 and tomosyn2 in the subareas of the mouse hippocampus. Using confocal and two-photon high-resolution microscopy we demonstrate that tomosyn colocalizes with several pre- and postsynaptic markers and is found mainly in glutamatergic synapses. Specifically, we show that tomosyn1 is differentially distributed in the mouse hippocampus and concentrated mainly in the hilus and mossy fibers. Surprisingly, we found that tomosyn2 is expressed in the subiculum, CA1 and CA2 pyramidal cell bodies, dendrites and spines, and colocalizes with PSD95, suggesting a postsynaptic role. These results suggest that in addition to the well-characterized presynaptic function of tomosyn in neurotransmitter release, tomosyn2 might have a postsynaptic function, and place tomosyn as a more general regulator of synaptic transmission and plasticity

Mechanisms underlying homeostatic plasticity in the Drosophila mushroom body in vivo

Neural network function requires an appropriate balance of excitation and inhibition to be maintained by homeostatic plasticity. However, little is known about homeostatic mechanisms in the intact central brain in vivo. Here, we study homeostatic plasticity in the Drosophila mushroom body, where Kenyon cells receive feedforward excitation from olfactory projection neurons and feedback inhibition from the anterior paired lateral neuron (APL). We show that prolonged (4-d) artificial activation of the inhibitory APL causes increased Kenyon cell odor responses after the artificial inhibition is removed, suggesting that the mushroom body compensates for excess inhibition. In contrast, there is little compensation for lack of inhibition (blockade of APL). The compensation occurs through a combination of increased excitation of Kenyon cells and decreased activation of APL, with differing relative contributions for different Kenyon cell subtypes. Our findings establish the fly mushroom body as a model for homeostatic plasticity in vivo

Effect of the DASH diet on the sodium-chloride cotransporter and aquaporin-2 in urinary extracellular vesicles

The dietary approach to stop hypertension (DASH) diet combines the antihypertensive effect of a low sodium and high potassium diet. In particular, the potassium component of the diet acts as a switch in the distal convoluted tubule to reduce sodium reabsorption, similar to a diuretic but without the side effects. Previous trials to understand the mechanism of the DASH diet were based on animal models and did not characterize changes in human ion channel protein abundance. More recently, protein cargo of urinary extracellular vesicles (uEVs) has been shown to mirror tissue content and physiological changes within the kidney. We designed an inpatient open label nutritional study transitioning hypertensive volunteers from an American style diet to DASH diet to examine physiological changes in adults with stage 1 hypertension otherwise untreated (Sacks FM, Svetkey LP, Vollmer WM, Appel LJ, Bray GA, Harsha D, Obarzanek E, Conlin PR, Miller ER 3rd, Simons-Morton DG, Karanja N, Lin PH; DASH-Sodium Collaborative Research Group. N Engl J Med 344: 3-10, 2001). Urine samples from this study were used for proteomic characterization of a large range of pure uEVs (small to large) to reveal kidney epithelium changes in response to the DASH diet. These samples were collected from nine volunteers at three time points, and mass spectrometry identified 1,800 proteins from all 27 samples. We demonstrated an increase in total SLC12A3 [sodium-chloride cotransporter (NCC)] abundance and a decrease in aquaporin-2 (AQP2) in uEVs with this mass spectrometry analysis, immunoblotting revealed a significant increase in the proportion of activated (phosphorylated) NCC to total NCC and a decrease in AQP2 from day 5 to day11. This data demonstrates that the human kidney's response to nutritional interventions may be captured noninvasively by uEV protein abundance changes. Future studies need to confirm these findings in a larger cohort and focus on which factor drove the changes in NCC and AQP2, to which degree NCC and AQP2 contributed to the antihypertensive effect and address if some uEVs function also as a waste pathway for functionally inactive proteins rather than mirroring protein changes.NEW &amp; NOTEWORTHY Numerous studies link DASH diet to lower blood pressure, but its mechanism is unclear. Urinary extracellular vesicles (uEVs) offer noninvasive insights, potentially replacing tissue sampling. Transitioning to DASH diet alters kidney transporters in our stage 1 hypertension cohort: AQP2 decreases, NCC increases in uEVs. This aligns with increased urine volume, reduced sodium reabsorption, and blood pressure decline. Our data highlight uEV protein changes as diet markers, suggesting some uEVs may function as waste pathways. We analyzed larger EVs alongside small EVs, and NCC in immunoblots across its molecular weight range.</p

Effect of the DASH diet on the sodium-chloride cotransporter and aquaporin-2 in urinary extracellular vesicles

The dietary approach to stop hypertension (DASH) diet combines the antihypertensive effect of a low sodium and high potassium diet. In particular, the potassium component of the diet acts as a switch in the distal convoluted tubule to reduce sodium reabsorption, similar to a diuretic but without the side effects. Previous trials to understand the mechanism of the DASH diet were based on animal models and did not characterize changes in human ion channel protein abundance. More recently, protein cargo of urinary extracellular vesicles (uEVs) has been shown to mirror tissue content and physiological changes within the kidney. We designed an inpatient open label nutritional study transitioning hypertensive volunteers from an American style diet to DASH diet to examine physiological changes in adults with stage 1 hypertension otherwise untreated (Sacks FM, Svetkey LP, Vollmer WM, Appel LJ, Bray GA, Harsha D, Obarzanek E, Conlin PR, Miller ER 3rd, Simons-Morton DG, Karanja N, Lin PH; DASH-Sodium Collaborative Research Group. N Engl J Med 344: 3-10, 2001). Urine samples from this study were used for proteomic characterization of a large range of pure uEVs (small to large) to reveal kidney epithelium changes in response to the DASH diet. These samples were collected from nine volunteers at three time points, and mass spectrometry identified 1,800 proteins from all 27 samples. We demonstrated an increase in total SLC12A3 [sodium-chloride cotransporter (NCC)] abundance and a decrease in aquaporin-2 (AQP2) in uEVs with this mass spectrometry analysis, immunoblotting revealed a significant increase in the proportion of activated (phosphorylated) NCC to total NCC and a decrease in AQP2 from day 5 to day11. This data demonstrates that the human kidney's response to nutritional interventions may be captured noninvasively by uEV protein abundance changes. Future studies need to confirm these findings in a larger cohort and focus on which factor drove the changes in NCC and AQP2, to which degree NCC and AQP2 contributed to the antihypertensive effect and address if some uEVs function also as a waste pathway for functionally inactive proteins rather than mirroring protein changes.NEW &amp; NOTEWORTHY Numerous studies link DASH diet to lower blood pressure, but its mechanism is unclear. Urinary extracellular vesicles (uEVs) offer noninvasive insights, potentially replacing tissue sampling. Transitioning to DASH diet alters kidney transporters in our stage 1 hypertension cohort: AQP2 decreases, NCC increases in uEVs. This aligns with increased urine volume, reduced sodium reabsorption, and blood pressure decline. Our data highlight uEV protein changes as diet markers, suggesting some uEVs may function as waste pathways. We analyzed larger EVs alongside small EVs, and NCC in immunoblots across its molecular weight range.</p