Purinergic receptor stimulation increases membrane trafficking in brown adipocytes.

Stimulation of brown adipocytes by their sympathetic innervation plays a major role in body energy homeostasis by regulating the energy-wasting activity of the tissue. The norepinephrine released by sympathetic activity acts on adrenergic receptors to activate a variety of metabolic and membrane responses. Since sympathetic stimulation may also release vesicular ATP, we tested brown fat cells for ATP responses. We find that micromolar concentrations of extracellular ATP initiates profound changes in the membrane trafficking of brown adipocytes. ATP elicited substantial increases in total cell membrane capacitance, averaging approximately 30% over basal levels and occurring on a time scale of seconds to minutes. The membrane capacitance increase showed an agonist sensitivity of 2-methylthio-ATP > or = ATP > ADP > > adenosine, consistent with mediation by a P2r type purinergic receptor. Membrane capacitance increases were not seen when cytosolic calcium was increased by adrenergic stimulation, and capacitance responses to ATP were similar in the presence and absence of extracellular calcium. These results indicate that increases in cytosolic calcium alone do not mediate the membrane response to ATP. Photometric assessment of surface-accessible membrane using the dye FM1-43 showed that ATP caused an approximate doubling of the amount of membrane actively trafficking with the cell surface. The discrepancy in the magnitudes of the capacitance and fluorescence changes suggests that ATP both activates exocytosis and alters other aspects of membrane handling. These findings suggest that secretion, mobilization of membrane transporters, and/or surface membrane expression of receptors may be regulated in brown adipocytes by P2r purinergic receptor activity.

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Effects of P2 purinergic receptor stimulation in brown adipocytes

AJP Cell Physiology ◽

10.1152/ajpcell.1997.273.2.c679 ◽

1997 ◽

Vol 273 (2) ◽

pp. C679-C686 ◽

Cited By ~ 30

Author(s):

S. C. Lee ◽

P. A. Pappone

Keyword(s):

Heat Production ◽

Purinergic Receptor ◽

Cytosolic Calcium ◽

Extracellular Atp ◽

Brown Fat ◽

Brown Adipocyte ◽

Fat Cells ◽

Sympathetic Stimulation ◽

Adrenergic Stimulation ◽

Brown Adipocytes

Sympathetic stimulation of brown adipocytes plays a major role in body energy homeostasis by activating energy-wasting pathways. Sympathetic neuronal input initiates a variety of metabolic, developmental, and membrane responses in brown fat cells. Many of these actions are mediated by adrenergic pathways mobilized by released norepinephrine. However, since sympathetic stimulation may also release vesicular ATP, we tested brown fat cells for ATP responses. Micromolar concentrations of extracellular ATP had a number of effects on brown adipocytes. We have shown previously that ATP elicits substantial (average of approximately 30%) increases in cell membrane capacitance (P. A. Pappone and S. C. Lee, J. Gen. Physiol. 108: 393-404, 1996). Here, we show that cytosolic calcium levels were increased by ATP, both through release from intracellular stores and through influx, as assessed by fura 2 imaging. In addition, ATP indirectly activated a nonselective cation conductance that was independent of cytosolic calcium levels in patch voltage-clamped brown fat cells. Similar calcium, conductance, and capacitance responses could be activated by 2-methylthio-ATP and ADP, consistent with mediation by a P2 type purinergic receptor. Calorimetric measurements from cell suspensions showed that ATP increased basal heat production of isolated brown fat cells by approximately 40% but had no effect on the greater than fivefold increase in heat production seen with maximal adrenergic stimulation. These myriad responses to extracellular ATP suggest that P2 receptor-mediated signaling is important in brown adipocyte physiology and that sympathetic stimulation may normally activate purinergic as well as adrenergic pathways in brown fat.

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Inducible brown adipocytes in subcutaneous inguinal white fat: the role of continuous sympathetic stimulation

AJP Endocrinology and Metabolism ◽

10.1152/ajpendo.00033.2014 ◽

2014 ◽

Vol 307 (9) ◽

pp. E793-E799 ◽

Cited By ~ 45

Author(s):

G. Andres Contreras ◽

Yun-Hee Lee ◽

Emilio P. Mottillo ◽

James G. Granneman

Keyword(s):

Adipose Tissue ◽

Uncoupling Protein ◽

Sympathetic Innervation ◽

Adrenergic Stimulation ◽

Brown Adipocytes ◽

Main Site ◽

Adipose Tissue Depots ◽

Brown Adipose ◽

White Fat

Brown adipocytes (BA) generate heat in response to sympathetic activation and are the main site of nonshivering thermogenesis in mammals. Although most BA are located in classic brown adipose tissue depots, BA are also abundant in the inguinal white adipose tissue (iWAT) before weaning. The number of BA is correlated with the density of sympathetic innervation in iWAT; however, the role of continuous sympathetic tone in the establishment and maintenance of BA in WAT has not been investigated. BA marker expression in iWAT was abundant in weaning mice but was greatly reduced by 8 wk of age. Nonetheless, BA phenotype could be rapidly reinstated by acute β3-adrenergic stimulation with CL-316,243 (CL). Genetic tagging of adipocytes with adiponectin-CreERT2 demonstrated that CL reinstates uncoupling protein 1 (UCP1) expression in adipocytes that were present before weaning. Chronic surgical denervation dramatically reduced the ability of CL to induce the expression of UCP1 and other BA markers in the tissue as a whole, and this loss of responsiveness was prevented by concurrent treatment with CL. These results indicate that ongoing sympathetic activity is critical to preserve the ability of iWAT fat cells to express a BA phenotype upon adrenergic stimulation.

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β-Adrenergic stimulation of interleukin-1α and interleukin-6 expression in mouse brown adipocytes

FEBS Letters ◽

10.1016/s0014-5793(97)00671-6 ◽

1997 ◽

Vol 411 (1) ◽

pp. 83-86 ◽

Cited By ~ 58

Author(s):

Ladislav Burýšek ◽

Josef Houštěk

Keyword(s):

Interleukin 6 ◽

Adrenergic Stimulation ◽

Brown Adipocytes ◽

Interleukin 1Α ◽

Stimulation Of

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Sympathetic Innervation of White Adipose Tissue: to Beige or Not to Beige?

Physiology ◽

10.1152/physiol.00038.2020 ◽

2021 ◽

Vol 36 (4) ◽

pp. 246-255

Author(s):

Heike Münzberg ◽

Elizabeth Floyd ◽

Ji Suk Chang

Keyword(s):

Adipose Tissue ◽

White Adipose Tissue ◽

Metabolic Regulation ◽

Current Knowledge ◽

Sympathetic Innervation ◽

Neuronal Circuits ◽

Brown Adipocytes ◽

White Adipocyte ◽

Obesity Research ◽

Neuronal Regulation

Obesity research progresses in understanding neuronal circuits and adipocyte biology to regulate metabolism. However, the interface of neuro-adipocyte interaction is less studied. We summarize the current knowledge of adipose tissue innervation and interaction with adipocytes and emphasize adipocyte transitions from white to brown adipocytes and vice versa. We further highlight emerging concepts for the differential neuronal regulation of brown/beige versus white adipocyte and the interdependence of both for metabolic regulation.

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Sex Hormones Regulate Rat Hepatic Monocarboxylate Transporter Expression and Membrane Trafficking

Journal of Pharmacy & Pharmaceutical Sciences ◽

10.18433/j3ch29 ◽

2017 ◽

Vol 20 (1) ◽

pp. 435 ◽

Cited By ~ 2

Author(s):

Jieyun Cao ◽

Michael Ng ◽

Melanie A Felmlee

Keyword(s):

Sex Differences ◽

Membrane Protein ◽

Protein Expression ◽

Estrous Cycle ◽

Sex Hormones ◽

Membrane Trafficking ◽

Drug Disposition ◽

Membrane Expression ◽

Membrane Protein Expression ◽

Estrous Cycle Stage

Purpose: Monocarboxylate transporters (MCTs) are involved in the transport of monocarboxylates such as ketone bodies, lactate, and pharmaceutical agents. CD147 functions as an ancillary protein for MCT1 and MCT4 for plasma membrane trafficking. Sex differences in MCT1 and MCT4 have been observed in muscle and reproductive tissues; however, there is a paucity of information on MCT sex differences in tissues involved in drug disposition. The objective of the present study was to quantify hepatic MCT1, MCT4 and CD147 mRNA, total cellular and membrane protein expression in males, over the estrous cycle in females and in ovariectomized (OVX) females. Method: Liver samples were collected from females at the four estrous cycle stages (proestrus, estrus, metestrus, diestrus), OVX females and male Sprague-Dawley rats (N = 3 – 5). Estrus cycle stage of females was determined by vaginal lavage. mRNA and protein (total and membrane) expression of MCT1, MCT4 and CD147 was evaluated by qPCR and western blot analysis. Results: MCT1 mRNA and membrane protein expression varied with estrous cycle stage, with OVX females having higher expression than males, indicating that female sex hormones may play a role in MCT1 regulation. MCT4 membrane expression varied with estrous cycle stage with expression significantly lower than males. MCT4 membrane expression in OVX females was also lower than males, suggesting that androgens play a role in membrane expression of MCT4. Males had higher membrane CD147 expression, whereas there was no difference in whole cell protein and mRNA levels suggesting that androgens are involved in regulating CD147 membrane localization. Conclusions: This study demonstrates hepatic expression and membrane localization of MCT1, MCT4 and CD147 are regulated by sex hormones. Sex differences in hepatic MCT expression may lead to altered drug disposition, so it is critical to elucidate the underlying mechanisms in the sex hormone-dependent regulation of MCT expression. This article is open to POST-PUBLICATION REVIEW. Registered readers (see “For Readers”) may comment by clicking on ABSTRACT on the issue’s contents page.

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The B cell IgM Fc receptor: further evidence for the B cell origin of "null" chronic lymphocytic leukemia

Blood ◽

10.1182/blood.v64.2.375.bloodjournal642375 ◽

1984 ◽

Vol 64 (2) ◽

pp. 375-379

Author(s):

RA Rudders ◽

PA Poldre

Keyword(s):

Cell Differentiation ◽

Chronic Lymphocytic Leukemia ◽

B Cell ◽

Surface Membrane ◽

Fc Receptor ◽

Lymphocytic Leukemia ◽

B Cell Differentiation ◽

Facs Analysis ◽

Membrane Expression ◽

Surface Immunoglobulin

Fifty-three cases of chronic lymphocytic leukemia (CLL) were studied for the presence of the B cell IgM Fc receptor (Fc microR) using an aggregated IgM reagent. Restricted surface immunoglobulin, using conventional immunofluorescent techniques and FACS analysis, was detected in 43 cases (81%). The cells in the remaining ten cases (19%) expressed negligible surface immunoglobulin (slg-) and did not form E rosettes (E-), but this “null” subset clearly expressed the B cell Fc microR. The coincident membrane expression of the B1 antigen and the la- like antigen, as well as serial studies showing surface membrane light chain acquisition (in one patient), provided additional evidence for the B cell origin of this slg-E- subset. This subgroup of CLL appears to correspond phenotypically to a normal counterpart at a stage of B cell differentiation between the pre-B cell and the slgM+ early B cell. The B cell Fc microR appears to be a consistent and potentially useful marker for sl gE (“null”) CLL.

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EHD2 regulates adipocyte function and is enriched at cell surface–associated lipid droplets in primary human adipocytes

Molecular Biology of the Cell ◽

10.1091/mbc.e18-10-0680 ◽

2019 ◽

Vol 30 (10) ◽

pp. 1147-1159 ◽

Cited By ~ 9

Author(s):

Björn Morén ◽

Björn Hansson ◽

Florentina Negoita ◽

Claes Fryklund ◽

Richard Lundmark ◽

...

Keyword(s):

Cell Surface ◽

Lipid Droplets ◽

Energy Homeostasis ◽

Lipid Uptake ◽

Human Adipocytes ◽

Adrenergic Stimulation ◽

Triglyceride Accumulation ◽

Aquaporin 7 ◽

Interfering Rna

Adipocytes play a central role in energy balance, and dysfunctional adipose tissue severely affects systemic energy homeostasis. The ATPase EH domain–containing 2 (EHD2) has previously been shown to regulate caveolae, plasma membrane-specific domains that are involved in lipid uptake and signal transduction. Here, we investigated the role of EHD2 in adipocyte function. We demonstrate that EHD2 protein expression is highly up-regulated at the onset of triglyceride accumulation during adipocyte differentiation. Small interfering RNA–mediated EHD2 silencing affected the differentiation process and impaired insulin sensitivity, lipid storage capacity, and lipolysis. Fluorescence imaging revealed localization of EHD2 to caveolae, close to cell surface–associated lipid droplets in primary human adipocytes. These lipid droplets stained positive for glycerol transporter aquaporin 7 and phosphorylated perilipin-1 following adrenergic stimulation. Further, EHD2 overexpression in human adipocytes increased the lipolytic signaling and suppressed the activity of transcription factor PPARγ. Overall, these data suggest that EHD2 plays a key role for adipocyte function.

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ATP induces contraction of cultured brain capillary pericytes, via activation of P2Y type purinergic receptors

AJP Heart and Circulatory Physiology ◽

10.1152/ajpheart.00560.2020 ◽

2020 ◽

Author(s):

Sofie Hørlyck ◽

Changsi Cai ◽

Hans C Helms ◽

Martin Lauritzen ◽

Birger Brodin

Keyword(s):

Intracellular Calcium ◽

Purinergic Receptors ◽

Calcium Release ◽

Purinergic Receptor ◽

Cytosolic Calcium ◽

Receptor Activation ◽

Confocal Imaging ◽

Inositol Triphosphate ◽

Brain Capillary

Brain capillary pericytes have been suggested to play a role in the regulation of cerebral blood-flow under physiological and pathophysiological conditions. ATP has been shown to cause constriction of capillaries under ischemic conditions and suggested to be involved in the "no-reflow" phenomenon. In order to investigate the effects of extracellular ATP on pericyte cell contraction, we studied purinergic receptor activation of cultured bovine brain capillary pericytes. We measured [Ca2+]i-responses to purinergic agonists with the fluorescent indicators fura-2 and Cal-520 and estimated contraction of pericytes as relative change in cell area, using real-time confocal imaging. Addition of ATP caused an increase in cytosolic calcium and contraction of the brain capillary pericytes, both reversible and inhibited by a purinergic receptor antagonist PPADS. Furthermore, we demonstrated that ATP-induced contraction could be eliminated by intracellular calcium-chelation with BAPTA, indicating that the contraction was mediated via purinergic P2 -type receptor-mediated [Ca2+]i-signaling. ATP stimulation induced inositol triphosphate signaling, consistent with the notion of P2Y receptor activation. Receptor profiling studies demonstrated presence of P2Y1 and P2Y2 receptors, using ATP, UTP, ADP and the subtype specific agonists MRS2365 (P2Y1) and 2-thio-UTP (P2Y2)). Addition of specific P2X agonists only caused a [Ca2+]i increase at high concentrations, attributed to activation of inositol triphosphate signaling. Our results suggest that contraction of brain capillary pericytes in vitro by activation of P2Y type purinergic receptors is caused by intracellular calcium release. This adds more mechanistic understanding to the role of pericytes in vessel constriction, and points towards P2Y receptors as potential therapeutic targets.

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