1
|
Qian S, Shi Y, Senfeld J, Peng Q, Shen J. The P2Y 2 receptor mediates terminal adipocyte differentiation and insulin resistance: Evidence for a dual G-protein coupling mode. J Biol Chem 2024; 300:105589. [PMID: 38141758 PMCID: PMC10828443 DOI: 10.1016/j.jbc.2023.105589] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2023] [Revised: 11/29/2023] [Accepted: 12/12/2023] [Indexed: 12/25/2023] Open
Abstract
Several P2Y nucleotide receptors have been shown to be involved in the early stage of adipocyte differentiation in vitro and insulin resistance in obese mice; however, the exact receptor subtype(s) and its underlying molecular mechanism in relevant human cells are unclear. Here, using human primary visceral preadipocytes as a model, we found that during preadipocyte-to-mature adipocyte differentiation, the P2Y2 nucleotide receptor (P2Y2R) was the most upregulated subtype among the eight known P2Y receptors and the only one further dramatically upregulated after inflammatory TNFα treatment. Functional studies indicated that the P2Y2R induced intracellular Ca2+, ERK1/2, and JNK signaling but not the p38 pathway. In addition, stimulation of the P2Y2R suppressed basal and insulin-induced phosphorylation of AKT, accompanied by decreased GLUT4 membrane translocation and glucose uptake in mature adipocytes, suggesting a role of P2Y2R in insulin resistance. Mechanistically, we found that activation of P2Y2R did not increase lipolysis but suppressed PIP3 generation. Interestingly, activation of P2Y2R triggered Gi-protein coupling, and pertussis toxin pretreatment largely inhibited P2Y2R-mediated ERK1/2 signaling and cAMP suppression. Further, treatment of the cells with AR-C 118925XX, a selective P2Y2R antagonist, significantly inhibited adipogenesis, and P2Y2R knockout decreased mouse body weight gain with smaller eWAT mass infiltrated with fewer macrophages as compared to WT mice in response to a Western diet. Thus, we revealed that terminal adipocyte differentiation and inflammation selectively upregulate P2Y2R expression and that P2Y2R mediates insulin resistance by suppressing the AKT signaling pathway, highlighting P2Y2R as a potential new drug target to combat obesity and type-2 diabetes.
Collapse
Affiliation(s)
- Shenqi Qian
- Department of Drug Discovery and Development, Harrison College of Pharmacy, Auburn University, Auburn, Alabama, USA; Department of Pharmacy, Second Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, China
| | - Yi Shi
- Department of Drug Discovery and Development, Harrison College of Pharmacy, Auburn University, Auburn, Alabama, USA
| | - Jared Senfeld
- Department of Drug Discovery and Development, Harrison College of Pharmacy, Auburn University, Auburn, Alabama, USA
| | - Qianman Peng
- Department of Drug Discovery and Development, Harrison College of Pharmacy, Auburn University, Auburn, Alabama, USA
| | - Jianzhong Shen
- Department of Drug Discovery and Development, Harrison College of Pharmacy, Auburn University, Auburn, Alabama, USA.
| |
Collapse
|
2
|
Activation of Cx43 Hemichannels Induces the Generation of Ca 2+ Oscillations in White Adipocytes and Stimulates Lipolysis. Int J Mol Sci 2021; 22:ijms22158095. [PMID: 34360859 PMCID: PMC8347185 DOI: 10.3390/ijms22158095] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2021] [Revised: 07/22/2021] [Accepted: 07/26/2021] [Indexed: 12/11/2022] Open
Abstract
The aim of the study was to investigate the mechanisms of Ca2+ oscillation generation upon activation of connexin-43 and regulation of the lipolysis/lipogenesis balance in white adipocytes through vesicular ATP release. With fluorescence microscopy it was revealed that a decrease in the concentration of extracellular calcium ([Ca2+]ex) results in two types of Ca2+ responses in white adipocytes: Ca2+ oscillations and transient Ca2+ signals. It was found that activation of the connexin half-channels is involved in the generation of Ca2+ oscillations, since the blockers of the connexin hemichannels-carbenoxolone, octanol, proadifen and Gap26-as well as Cx43 gene knockdown led to complete suppression of these signals. The activation of Cx43 in response to the reduction of [Ca2+]ex was confirmed by TIRF microscopy. It was shown that in response to the activation of Cx43, ATP-containing vesicles were released from the adipocytes. This process was suppressed by knockdown of the Cx43 gene and by bafilomycin A1, an inhibitor of vacuolar ATPase. At the level of intracellular signaling, the generation of Ca2+ oscillations in white adipocytes in response to a decrease in [Ca2+]ex occurred due to the mobilization of the Ca2+ ions from the thapsigargin-sensitive Ca2+ pool of IP3R as a result of activation of the purinergic P2Y1 receptors and phosphoinositide signaling pathway. After activation of Cx43 and generation of the Ca2+ oscillations, changes in the expression levels of key genes and their encoding proteins involved in the regulation of lipolysis were observed in white adipocytes. This effect was accompanied by a decrease in the number of adipocytes containing lipid droplets, while inhibition or knockdown of Cx43 led to inhibition of lipolysis and accumulation of lipid droplets. In this study, we investigated the mechanism of Ca2+ oscillation generation in white adipocytes in response to a decrease in the concentration of Ca2+ ions in the external environment and established an interplay between periodic Ca2+ modes and the regulation of the lipolysis/lipogenesis balance.
Collapse
|
3
|
Jain S, Jacobson KA. Purinergic signaling in diabetes and metabolism. Biochem Pharmacol 2020; 187:114393. [PMID: 33359363 DOI: 10.1016/j.bcp.2020.114393] [Citation(s) in RCA: 34] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2020] [Revised: 12/21/2020] [Accepted: 12/22/2020] [Indexed: 12/22/2022]
Abstract
Purinergic signaling, a concept originally formulated by the late Geoffrey Burnstock (1929-2020), was found to modulate pathways in every physiological system. In metabolic disorders there is a role for both adenosine receptors and P2 (nucleotide) receptors, of which there are two classes, i.e. P2Y metabotropic and P2X ionotropic receptors. The individual roles of the 19 receptors encompassed by this family have been dissected - and in many cases the effects associated with specific cell types, including adipocytes, skeletal muscle, liver cells and immune cells. It is suggested that ligands selective for each of the four adenosine receptors (A1, A2A, A2B and A3), and several of the P2 subtypes (e.g. P2Y6 or P2X7 antagonists) might have therapeutic potential for treating diabetes and obesity. This is a developing story with some conflicting conclusions relevant to drug discovery, which we summarize here.
Collapse
Affiliation(s)
- Shanu Jain
- Molecular Recognition Section, Laboratory of Bioorganic Chemistry, National Institute of Diabetes and Digestive and Kidney Diseases, Bethesda, MD 20892, USA
| | - Kenneth A Jacobson
- Molecular Recognition Section, Laboratory of Bioorganic Chemistry, National Institute of Diabetes and Digestive and Kidney Diseases, Bethesda, MD 20892, USA.
| |
Collapse
|
4
|
Tozzi M, Novak I. Purinergic Receptors in Adipose Tissue As Potential Targets in Metabolic Disorders. Front Pharmacol 2017; 8:878. [PMID: 29249968 PMCID: PMC5715378 DOI: 10.3389/fphar.2017.00878] [Citation(s) in RCA: 59] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2017] [Accepted: 11/13/2017] [Indexed: 01/04/2023] Open
Abstract
Extracellular nucleosides and nucleotides, such as adenosine and adenosine triphosphate (ATP), are involved in many physiological and pathological processes in adipose tissue (AT). It is becoming accepted that, in addition to the well-established sympathetic and hormonal system, purinergic receptors contribute significantly to regulation of adipocyte functions. Several receptor subtypes for both adenosine (P1) and ATP (P2X and P2Y) have been characterized in white adipocytes (WA) and brown adipocytes (BA). The effects mediated by adenosine and ATP on adipocytes are multiple and often differing, depending on specific receptors activated. Using a variety of agonists, antagonists and transgenic animals it has been demonstrated that adenosine and P2 receptors are involved in lipolysis, lipogenesis, adipokines secretion, glucose uptake, adipogenesis, cell proliferation, inflammation, and other processes. Given their central role in regulating many AT functions, purinergic receptors are considered potential therapeutic targets in different pathological conditions, such as obesity and type-2 diabetes. To achieve this goal, specific and potent P1 and P2 receptors activators and inhibitors are being developed and show promising results. However, more insight is needed into the function of P2 receptors in brown and beige adipocytes and their potential role in thermogenesis. This review aims at summarizing current knowledge on the patho-/physiological role of P1, P2X, and P2Y receptors in WA and BA and their potential exploitation for pharmacological intervention. Furthermore, we analyze impact of purinergic signaling in AT - in health and metabolic diseases.
Collapse
Affiliation(s)
- Marco Tozzi
- Section for Cell Biology and Physiology, Department of Biology, University of Copenhagen, Copenhagen, Denmark
| | - Ivana Novak
- Section for Cell Biology and Physiology, Department of Biology, University of Copenhagen, Copenhagen, Denmark
| |
Collapse
|
5
|
Pannexin 1 is required for full activation of insulin-stimulated glucose uptake in adipocytes. Mol Metab 2015; 4:610-8. [PMID: 26413467 PMCID: PMC4563021 DOI: 10.1016/j.molmet.2015.06.009] [Citation(s) in RCA: 48] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/20/2015] [Accepted: 06/27/2015] [Indexed: 02/08/2023] Open
Abstract
Objective Defective glucose uptake in adipocytes leads to impaired metabolic homeostasis and insulin resistance, hallmarks of type 2 diabetes. Extracellular ATP-derived nucleotides and nucleosides are important regulators of adipocyte function, but the pathway for controlled ATP release from adipocytes is unknown. Here, we investigated whether Pannexin 1 (Panx1) channels control ATP release from adipocytes and contribute to metabolic homeostasis. Methods We assessed Panx1 functionality in cultured 3T3-L1 adipocytes and in adipocytes isolated from murine white adipose tissue by measuring ATP release in response to known activators of Panx1 channels. Glucose uptake in cultured 3T3-L1 adipocytes was measured in the presence of Panx1 pharmacologic inhibitors and in adipocytes isolated from white adipose tissue from wildtype (WT) or adipocyte-specific Panx1 knockout (AdipPanx1 KO) mice generated in our laboratory. We performed in vivo glucose uptake studies in chow fed WT and AdipPanx1 KO mice and assessed insulin resistance in WT and AdipPanx1 KO mice fed a high fat diet for 12 weeks. Panx1 channel function was assessed in response to insulin by performing electrophysiologic recordings in a heterologous expression system. Finally, we measured Panx1 mRNA in human visceral adipose tissue samples by qRT-PCR and compared expression levels with glucose levels and HOMA-IR measurements in patients. Results Our data show that adipocytes express functional Pannexin 1 (Panx1) channels that can be activated to release ATP. Pharmacologic inhibition or selective genetic deletion of Panx1 from adipocytes decreased insulin-induced glucose uptake in vitro and in vivo and exacerbated diet-induced insulin resistance in mice. Further, we identify insulin as a novel activator of Panx1 channels. In obese humans Panx1 expression in adipose tissue is increased and correlates with the degree of insulin resistance. Conclusions We show that Panx1 channel activity regulates insulin-stimulated glucose uptake in adipocytes and thus contributes to control of metabolic homeostasis. Adipocytes express Pannexin 1 channels that can be activated to release ATP. Inhibition of Pannexin 1 decreased insulin-induced glucose uptake in adipocytes. Adipocyte Pannexin 1 knockout mice are more insulin resistant on high fat diet. We identify insulin as a novel activator of Pannexin 1 channels. Pannexin 1 expression in human adipose tissue correlates with insulin resistance.
Collapse
|
6
|
Burnstock G. Purinergic signalling in endocrine organs. Purinergic Signal 2014; 10:189-231. [PMID: 24265070 PMCID: PMC3944044 DOI: 10.1007/s11302-013-9396-x] [Citation(s) in RCA: 57] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2013] [Accepted: 10/24/2013] [Indexed: 01/08/2023] Open
Abstract
There is widespread involvement of purinergic signalling in endocrine biology. Pituitary cells express P1, P2X and P2Y receptor subtypes to mediate hormone release. Adenosine 5'-triphosphate (ATP) regulates insulin release in the pancreas and is involved in the secretion of thyroid hormones. ATP plays a major role in the synthesis, storage and release of catecholamines from the adrenal gland. In the ovary purinoceptors mediate gonadotrophin-induced progesterone secretion, while in the testes, both Sertoli and Leydig cells express purinoceptors that mediate secretion of oestradiol and testosterone, respectively. ATP released as a cotransmitter with noradrenaline is involved in activities of the pineal gland and in the neuroendocrine control of the thymus. In the hypothalamus, ATP and adenosine stimulate or modulate the release of luteinising hormone-releasing hormone, as well as arginine-vasopressin and oxytocin. Functionally active P2X and P2Y receptors have been identified on human placental syncytiotrophoblast cells and on neuroendocrine cells in the lung, skin, prostate and intestine. Adipocytes have been recognised recently to have endocrine function involving purinoceptors.
Collapse
Affiliation(s)
- Geoffrey Burnstock
- Autonomic Neuroscience Centre, University College Medical School, Rowland Hill Street, London, NW3 2PF, UK,
| |
Collapse
|
7
|
Mohan S, Sheena A, Poulose N, Anilkumar G. Molecular dynamics simulation studies of GLUT4: substrate-free and substrate-induced dynamics and ATP-mediated glucose transport inhibition. PLoS One 2010; 5:e14217. [PMID: 21151967 PMCID: PMC2997047 DOI: 10.1371/journal.pone.0014217] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2010] [Accepted: 11/15/2010] [Indexed: 02/03/2023] Open
Abstract
Background Glucose transporter 4 (GLUT4) is an insulin facilitated glucose transporter that plays an important role in maintaining blood glucose homeostasis. GLUT4 is sequestered into intracellular vesicles in unstimulated cells and translocated to the plasma membrane by various stimuli. Understanding the structural details of GLUT4 will provide insights into the mechanism of glucose transport and its regulation. To date, a crystal structure for GLUT4 is not available. However, earlier work from our laboratory proposed a well validated homology model for GLUT4 based on the experimental data available on GLUT1 and the crystal structure data obtained from the glycerol 3-phosphate transporter. Methodology/Principal Findings In the present study, the dynamic behavior of GLUT4 in a membrane environment was analyzed using three forms of GLUT4 (apo, substrate and ATP-substrate bound states). Apo form simulation analysis revealed an extracellular open conformation of GLUT4 in the membrane favoring easy exofacial binding of substrate. Simulation studies with the substrate bound form proposed a stable state of GLUT4 with glucose, which can be a substrate-occluded state of the transporter. Principal component analysis suggested a clockwise movement for the domains in the apo form, whereas ATP substrate-bound form induced an anti-clockwise rotation. Simulation studies suggested distinct conformational changes for the GLUT4 domains in the ATP substrate-bound form and favor a constricted behavior for the transport channel. Various inter-domain hydrogen bonds and switching of a salt-bridge network from E345-R350-E409 to E345-R169-E409 contributed to this ATP-mediated channel constriction favoring substrate occlusion and prevention of its release into cytoplasm. These data are consistent with the biochemical studies, suggesting an inhibitory role for ATP in GLUT-mediated glucose transport. Conclusions/Significance In the absence of a crystal structure for any glucose transporter, this study provides mechanistic details of the conformational changes in GLUT4 induced by substrate and its regulator.
Collapse
Affiliation(s)
- Suma Mohan
- Amrita School of Biotechnology, Amrita Vishwa Vidyapeetham, Kollam, Kerala, India
| | - Aswathy Sheena
- Amrita School of Biotechnology, Amrita Vishwa Vidyapeetham, Kollam, Kerala, India
| | - Ninu Poulose
- Amrita School of Biotechnology, Amrita Vishwa Vidyapeetham, Kollam, Kerala, India
| | | |
Collapse
|
8
|
Krall JF, Korenman SG. Control of uterine contractility via cyclic AMP-dependent protein kinase. CIBA FOUNDATION SYMPOSIUM 2008:319-41. [PMID: 205395 DOI: 10.1002/9780470720295.ch13] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
|
9
|
Schneider W, Gear AR. Significance of glucose and glycogen metabolism for platelet function. CIBA FOUNDATION SYMPOSIUM 2008; 35:225-38. [PMID: 179767 DOI: 10.1002/9780470720172.ch11] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
|
10
|
Burnstock G, Knight GE. Cellular Distribution and Functions of P2 Receptor Subtypes in Different Systems. INTERNATIONAL REVIEW OF CYTOLOGY 2004; 240:31-304. [PMID: 15548415 DOI: 10.1016/s0074-7696(04)40002-3] [Citation(s) in RCA: 581] [Impact Index Per Article: 29.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
This review is aimed at providing readers with a comprehensive reference article about the distribution and function of P2 receptors in all the organs, tissues, and cells in the body. Each section provides an account of the early history of purinergic signaling in the organ?cell up to 1994, then summarizes subsequent evidence for the presence of P2X and P2Y receptor subtype mRNA and proteins as well as functional data, all fully referenced. A section is included describing the plasticity of expression of P2 receptors during development and aging as well as in various pathophysiological conditions. Finally, there is some discussion of possible future developments in the purinergic signaling field.
Collapse
Affiliation(s)
- Geoffrey Burnstock
- Autonomic Neuroscience Institute, Royal Free and University College Medical School, London NW3 2PF, United Kingdom
| | | |
Collapse
|
11
|
Lee SC, Pappone PA. ATP can stimulate exocytosis in rat brown adipocytes without apparent increases in cytosolic Ca2+ or G protein activation. Biophys J 1999; 76:2297-306. [PMID: 10096924 PMCID: PMC1300202 DOI: 10.1016/s0006-3495(99)77385-6] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Extracellular ATP activates large increases in cell surface area and membrane turnover in rat brown adipocytes (Pappone, P. A., and Lee, S. C. 1996. J. Gen. Physiol. 108:393-404). We used whole-cell patch clamp membrane capacitance measurements of membrane surface area concurrently with fura-2 ratio imaging of intracellular calcium to test whether these purinergic membrane responses are triggered by cytosolic calcium increases or G protein activation. Increasing cytosolic calcium with adrenergic stimulation, calcium ionophore, or calcium-containing pipette solutions did not cause exocytosis. Extracellular ATP increased membrane capacitance in the absence of extracellular calcium with internal calcium strongly buffered to near resting levels. Purinergic stimulation still activated exocytosis and endocytosis in the complete absence of intracellular and extracellular free calcium, but endocytosis predominated. Modulators of G protein function neither triggered nor inhibited the initial ATP-elicited capacitance changes, but GTPgammaS or cytosolic nucleotide depletion did reduce the cells' capacity to mount multiple purinergic responses. These results suggest that calcium modulates purinergically-stimulated membrane trafficking in brown adipocytes, but that ATP responses are initiated by some other signal that remains to be identified.
Collapse
Affiliation(s)
- S C Lee
- Section of Neurobiology, Physiology, and Behavior, University of California, Davis, California 95616, USA
| | | |
Collapse
|
12
|
Eblenkamp M, Böttcher U, Thomas J, Löken C, Ionescu I, Rose H, Kammermeier H, Fischer Y. The effect of anoxia on cardiomyocyte glucose transport does not involve an adenosine release or a change in energy state. Life Sci 1996; 59:141-51. [PMID: 8699921 DOI: 10.1016/0024-3205(96)00270-6] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
The action of anoxia on glucose transport was investigated in isolated resting rat cardiomyocytes. Incubation of these cells in the absence of oxygen for 30 min resulted in a 4- to 5-fold increase in glucose transport (with a lag period of 5-10 min). Up to 40 min of anoxia failed to alter the cellular concentrations of ATP, phosphocreatine, and creatine. Adenosine deaminase (1.5 U/ml), the A1-adenosine receptor antagonist 1,3-diethyl-8-phenylxanthine (1 microM), or the A2-selective antagonist 3,7-dimethyl-1-propargylxanthine (20 microM) had no effect on anoxia-dependent glucose transport. Moreover, adenosine (10-300 microM, added under normoxia) did not stimulate glucose transport. Wortmannin (1 microM) did not influence the effect of anoxia, but completely suppressed that of insulin. On the other hand, the effects of anoxia and insulin were not additive. These results indicate (i) that the effect of anoxia on cardiomyocyte glucose transport is not mediated by a change in energy metabolism, nor by an adenosine release; (ii) that it probably does not involve a phosphatidylinositol 3-kinase, in contrast to the effect of insulin, and (iii) that the signal chains triggered by anoxia or insulin may converge downstream of this enzyme, or, alternatively, that anoxic conditions may impair the action of the hormone.
Collapse
|
13
|
Shibata H, Robinson FW, Benzing CF, Kono T. Evidence that protein kinase C may not be involved in the insulin action on cAMP phosphodiesterase: studies with electroporated rat adipocytes that were highly responsive to insulin. Arch Biochem Biophys 1991; 285:97-104. [PMID: 1846737 DOI: 10.1016/0003-9861(91)90333-e] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Partially permeabilized rat adipocytes with a high responsiveness to insulin were prepared by electroporation and used to study the effect of 1-(5-isoquinolinylsulfonyl)-2-methylpiperazine (H-7) on insulin actions in adipocytes. H-7 is a well-documented inhibitor of several protein kinases, including protein kinase C; however, it does not rapidly enter adipocytes protected with the intact plasma membrane. The cells were suspended in Buffer X [4.74 mM NaCl, 118.0 mM KCl, 0.38 mM CaCl2, 1.00 mM EGTA, 1.19 mM Mg2SO4, 1.19 mM KH2PO4, 25.0 mM Hepes/K, 20 mg/ml bovine serum albumin, and 3 mM pyruvate/Na, pH 7.4] and electroporated six times with a Gene-Pulser (from Bio-Rad) set at 25 microF and 2 kV/cm. In cells electroporated as above, insulin stimulated (a) membrane-bound, cAMP phosphodiesterase approximately 2.6-fold when the hormone concentration was 10 nM and (b) glucose transport activity approximately 4.5-fold when the hormone concentration was raised to 100 nM. H-7 strongly inhibited the actions of insulin on both glucose transport (apparent Ki = 0.3 mM) and cAMP phosphodiesterase (apparent Ki = 1.2 mM) in electroporated adipocytes. H-7 also inhibited lipolysis in adipocytes; the apparent Ki value for the reaction in intact cells was 0.45 mM, and that in electroporated cells was 0.075 mM. It is suggested that a certain protein kinase or kinases that are significantly sensitive to H-7 may be involved in the insulin-dependent stimulation of glucose transport and that of phosphodiesterase. However, protein kinase C (or Ca2+/phospholipid-dependent protein kinase) may not be involved, at least, in the hormonal action on phosphodiesterase since the apparent Ki value of H-7 for the reaction is too high.
Collapse
Affiliation(s)
- H Shibata
- Department of Molecular Physiology and Biophysics, School of Medicine, Vanderbilt University, Nashville, Tennessee 37232-0615
| | | | | | | |
Collapse
|
14
|
|
15
|
Boynton AL, Cooney RV, Hill TD, Nilsson T, Arkhammar P, Berggren PO. Extracellular ATP mobilizes intracellular Ca2+ in T51B rat liver epithelial cells: a study involving single cell measurements. Exp Cell Res 1989; 181:245-55. [PMID: 2783910 DOI: 10.1016/0014-4827(89)90198-5] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
T51B rat liver epithelial cells were stimulated with extracellular ATP. Changes in cytoplasmic free Ca2+ concentration [( Ca2+]i) were measured by fura-2 both in a large population of cells on coverslips in a cuvette and in single cells in a microscopic system. Extracellular ATP evoked a prompt increase in [Ca2+]i in both the presence and absence of extracellular Ca2+, although the effect was less pronounced in the latter case. These findings indicate that at least part of the [Ca2+]i increase is due to mobilization of intracellularly bound calcium. Stimulation with ATP did not mobilize the total pool of intracellular releasable Ca2+, as evidenced from experiments where subsequent addition of ionomycin evoked a pronounced increase in [Ca2+]i in the absence of extracellular Ca2+. The effect of ATP was maintained at room temperature but was markedly impaired in the absence of continuous stirring of the buffer solution. In the absence of stirring, ATP had to be increased to the millimolar range in order to evoke a pronounced effect. Single cell measurements revealed a heterogenous Ca2+ response to ATP, with some cells failing to respond with a detectable increase in [Ca2+]i. The actual increase in [Ca2+]i was not uniform throughout the cytoplasm, but seemed to start in one part of the cell. Even if part of the [Ca2+]i increase might be accounted for by ATP promoting the hydrolysis of phosphatidylinositol 4,5-bisphosphate and thereby a generation of InsP3 and diacylglycerol, there was no initiation of DNA synthesis under the present conditions. Hence, extracellular growth factors exert either a quantitative difference in second messenger production or additional stimulatory effects by activating intracellular signal pathways beyond these represented by [Ca2+]i and protein kinase C.
Collapse
Affiliation(s)
- A L Boynton
- Cancer Research Center of Hawaii, Honolulu 96813
| | | | | | | | | | | |
Collapse
|
16
|
Shechter Y, Meyerovitch J, Amir S. The use of post-binding agents in studying insulin action and its relation to experimental diabetes. Biochem Pharmacol 1988; 37:1891-6. [PMID: 2837217 DOI: 10.1016/0006-2952(88)90533-3] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
This review includes data related to two substances that modulate insulin mechanisms, both in vitro and in the whole animal model. It seems to us that these agents (vanadate and PMXB) will be of potential use in the next decade for basic and applied research. They may assist in characterizing the essential post-binding events involved in insulin action, which cannot presently be identified. As vanadate and PMXB modulate the effects of insulin both in vivo and in vitro, they may be of use in clinical and pathophysiological research as well. VO3- is a low molecular weight substance which permeates the intestinal tract and mimics the actions of insulin in target tissues. Studies that were summarized here may even suggest that VO3- is superior to insulin in stimulating its effects in tissues that are down-regulated or desensitized to the hormone itself. Both VO3- and PMXB may be useful in the treatment of diabetes in the future if long-range toxicity studies prove these agents to be clinically safe. PMXB has already been in use in medicine for several decades now.
Collapse
Affiliation(s)
- Y Shechter
- Department of Hormone Research, Weizmann Institute of Science, Rehovot, Israel
| | | | | |
Collapse
|
17
|
|
18
|
Hashimoto N, Robinson FW, Shibata Y, Flanagan JE, Kono T. Diversity in the effects of extracellular ATP and adenosine on the cellular processing and physiologic actions of insulin in rat adipocytes. J Biol Chem 1987. [DOI: 10.1016/s0021-9258(18)48132-x] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
|
19
|
Morenkova SA. Mechanism of hyperglycemia induced by extensive wounds and generalized surgical infection. ACTA DIABETOLOGICA LATINA 1987; 24:119-32. [PMID: 3307258 DOI: 10.1007/bf02742850] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Significant differences were revealed in the mechanism of hyperglycemia in extensive wounds and generalized surgical infection. Hyperglycemia in extensive burn injuries is caused by the inhibition of insulin formation, decreased insulin binding to cellular receptors, which leads to decreased sensitivity of tissues to insulin. Hyperglycemia developing in generalized infection is a result of insufficient blood insulin levels consequent to inhibition of its secretion (while insulin biosynthesis is elevated) under the effects of hyperproduction of prostaglandins, and is also mediated by defects in insulin-receptor interaction. Correction of carbohydrate metabolism disorders in these surgical pathologies in spite of the different pathogenetic mechanisms might be achieved by exogenous insulin administration, and also by insulin administration together with indomethacin, a nonsteroid anti-inflammatory agent, inhibiting prostaglandin production.
Collapse
|
20
|
Estrela JM, Montoro JB, Viña JR, Viña J. Glutathione metabolism under the influence of hydroperoxides in the lactating mammary gland of the rat. Effect of glucose and extracellular ATP. Biosci Rep 1987; 7:23-31. [PMID: 3620601 DOI: 10.1007/bf01122724] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
Tert-butyl hydroperoxide decreases GSH and total free glutathione (GSH + 2GSSG) contents of acini from lactating mammary glands. The decrease in total free glutathione can be explained by an increase in mixed disulfide formation and by excretion of GSSG to the extracellular medium, and subsequent degradation catalyzed by gamma-glutamyl transpeptidase. Low concentrations of glucose prevented the changes in glutathione levels induced by the peroxide. In the presence of extracellular ATP, glucose did not prevent these changes. However, incubations with the peroxide, did not alter the rate of other metabolic pathways by acini.
Collapse
|
21
|
Kang ES, Chiang TM. Characterization of the major phosphoprotein and its kinase on the surface of the rat adipocyte. Exp Cell Res 1986; 167:343-59. [PMID: 3770093 DOI: 10.1016/0014-4827(86)90175-8] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Intact rat fat cells exposed to 12.5 microM [gamma-32P]ATP incorporate label into specific proteins within minutes. By solubilizing the reaction mixture with SDS which by passes the subcellular fractionation steps, the labeled proteins can be identified in autoradiographs of SDS-PAGE gels. The most prominently labeled protein has an Mr of 42,000. Localization of this component to the cell surface can be made on the basis of inhibition of phosphorylation by addition of a protein derived from the rat brain with protein kinase inhibitory property, susceptibility of the phosphorylated protein to tryptic digestion, whereas the unphosphorylated protein is unaffected by digestion with trypsin (15 min), inhibition of phosphorylation of this protein after brief exposure to melittin, and the consistent observation that more label is associated with the 42,000 Mr band in homogenates and permeabilized cells than in comparable numbers of intact cells exposed to the same amount of label. A 42,000 Mr phosphoprotein is also present in mitochondria which is most likely the alpha subunit of pyruvate dehydrogenase. To rule out the possibility that the cell surface protein might be a mitochondrial contaminant from broken cells, 32Pi-labeled and [gamma-32P]ATP-labeled cells were solubilized with Triton and chromatographed on a rabbit anti-pyruvate dehydrogenase antibody-Sepharose 4B column. A single labeled peak was detected upon elution of the bound fraction only in the 32Pi-labeled sample, and not in the [gamma-32P]ATP-labeled sample. Subcellular fractionation studies of intact cells labeled with [gamma-32P]ATP showed differences in the recovery of phosphoproteins of 42,000 Mr depending on whether a continuous sucrose gradient (27.6-54.1%, g/ml) or a discontinuous sucrose gradient (16, 35 and 48%, g/ml) was used. Phosphoproteins of 42,000 Mr were located in the mitochondrial and membrane fractions collected by discontinuous sucrose gradient separation, whereas a phosphoprotein of 42,000 Mr was found primarily in the mitochondrial fraction after continuous sucrose gradient separation. By 5'-nucleotidase activity measurements, the latter approach appears to result in the isolation of a heavy fragment of the plasma membrane with the mitochondrial light fraction which is 42,000 in Mr and labeled. Finally, comparison of the autoradiographs of two-dimensional (2D) gels (isoelectric focusing followed by 10% SDS-PAGE) show different isoelectric points for 42,000 Mr components in [gamma-32P]ATP- and 32Pi-labeled cells.(ABSTRACT TRUNCATED AT 400 WORDS)
Collapse
|
22
|
Chiang TM, Kang AH. Identification, purification, and partial characterization of plasma protein kinases. Arch Biochem Biophys 1985; 243:530-41. [PMID: 4083899 DOI: 10.1016/0003-9861(85)90530-2] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Two isomeric forms of protein kinases, FI and FII, were isolated from human plasma. These two isomeric enzymes were isolated to apparent homogeneity on NaDodSO4-PAGE by using (NH4)2SO4 fractionation, DEAE-cellulose, hydroxylapatite, Affi-Gel blue, and high-pressure liquid column chromatography. Polyclonal antibodies were obtained from immunized rabbits and both enzymes cross-reacted with each other. Furthermore, immunoaffinity-purified anti-FI and anti-FII antibodies inhibited the enzyme activity of both FI and FII. These enzymes are cyclic nucleotides, Ca2+, calmodulin and phosphatidylserine-independent enzymes which can phosphorylate exogenously added histone, casein, protamine, phosvitin, and platelet surface proteins. The phosphorylated proteins of intact platelets by these enzymes in the presence of exogenously added [gamma-32P]ATP ranged in apparent molecular weights from 13.5K to 200K, as estimated by their mobility during NaDodSO4-PAGE. Trypsin removed the label from the platelet surface phosphoproteins without affecting the intracellularly located phosphoproteins labeled endogenously by 32PO4-prelabeling of intact platelets. These observations raise the possibility that these enzymes could play a role in modulating the properties of platelets through phosphorylation of the platelet surface proteins.
Collapse
|
23
|
Friedberg I, Weisman GA, De BK. Permeability change in transformed mouse fibroblasts caused by ionophores, and its relationship to membrane permeabilization by exogenous ATP. J Membr Biol 1985; 83:251-9. [PMID: 3999123 DOI: 10.1007/bf01868699] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Electrogenic ionophores have been found to induce membrane permeabilization in Swiss mouse 3T3 cells that had undergone spontaneous transformation (3T6 cells). Cells attached to plastic dishes were loaded with [3H] uridine, and then the medium was replaced by buffered salt solution at pH 7.8. The enhancement of membrane permeability was assayed by following the efflux of uridine nucleotides, normally impermeant substances. Titration with electrogenic ionophores, such as carbonylcyanide m-chlorophenylhydrazone (CCCP), SF-6847 and gramicidin D, markedly increased the membrane permeability within a very narrow range of ionophore concentration. Non-electrogenic ionophores, such as monensin and nigericin, did not affect membrane permeability. Measurements of the distribution of the lipophilic cation tetraphenylphosphonium (TPP+) between the cells and their environment implied that the remarkable increase in permeability took place within a narrow range of membrane potential (delta psi). The data could be explained by a delta psi threshold value, under which aqueous channels are opened in the plasma membrane. The effects exerted by electrogenic ionophores on the plasma membrane were found to be similar to those induced by exogenous ATP. In both cases rapid efflux of K+, influx of Na+ and reduction of delta psi preceded membrane permeabilization to low molecular weight, charged molecules, such as nucleotides. It is suggested that dissipation of delta psi induces conformational alterations in membranal components, and/or topological changes, such as aggregation of protein molecules, to form membranal aqueous channels. Electrogenic ionophores permeabilize both normal (3T3) and transformed (3T6) mouse fibroblasts, whereas ATP effects are specific for transformed cells. Thus, it is postulated that ATP acts via specific sites on the surface of transformed cells.
Collapse
|
24
|
Dubyak GR, De Young MB. Intracellular Ca2+ mobilization activated by extracellular ATP in Ehrlich ascites tumor cells. J Biol Chem 1985. [DOI: 10.1016/s0021-9258(19)85134-7] [Citation(s) in RCA: 87] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
|
25
|
Multiple roles of ATP in the regulation of sugar transport in muscle and adipose tissue. Trends Biochem Sci 1984. [DOI: 10.1016/0968-0004(84)90281-0] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
|
26
|
Amano F, Kitagawa T, Akamatsu Y. Protein kinase activity on the cell surface of a macrophage-like cell line, J774.1 cells. BIOCHIMICA ET BIOPHYSICA ACTA 1984; 803:163-73. [PMID: 6704429 DOI: 10.1016/0167-4889(84)90006-5] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
Protein kinase activity was demonstrated on the cell surface of a murine macrophage-like cell line, J774.1 cells, and was characterized in detail. When intact cells were incubated with [gamma-32P]ATP, a transfer of [32P]phosphate into acid-insoluble materials of the cells occurred. This reaction was Mg2+-dependent but cAMP-independent, and Mg2+ could be substituted for by Mn2+. The reaction products were found to be proteins, as revealed by SDS-polyacrylamide gel electrophoresis and autoradiography, with phosphomonester linkages to serine and threonine residues, but not to tyrosine. The results of experiments with chemical and enzymatic treatments as well as Con A-Sepharose column chromatography ruled out the possibility that an acyl-phosphate linkage or phosphomannosylglycopeptide was present in the reaction products. The protein kinase(s) and the reaction products were located on the cell surface of the cells, as shown by the fact that the products were removed by mild trypsinization of cells carefully controlled so that the cells remained in an intact state. Phosphorylation of exogenous proteins (phosvitin and casein) by intact cells further supported the location of the enzyme. The phosphorylated proteins of the cells were found to be metabolically stable and remained on the cell surface even at 120 min after the phosphorylation reaction. Possible roles of ecto-protein kinase activity in macrophage functions and macrophage-activation are also discussed.
Collapse
|
27
|
Wieringa T, Bos MP, van Putten JP, Krans HM. Stimulatory and inhibitory effects of adrenaline and 8-bromo-cAMP on insulin-sensitive 2-deoxyglucose transport in rat adipocytes. BIOCHIMICA ET BIOPHYSICA ACTA 1984; 803:129-36. [PMID: 6367831 DOI: 10.1016/0167-4889(84)90002-8] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
The effects of adrenaline and 8-bromo-cAMP on 2-deoxyglucose uptake in isolated rat adipocytes were investigated under conditions of unidirectional flux, in which the transport process is rate limiting. Adrenaline showed a dualistic effect in the absence of insulin. At concentrations below 1 microM adrenaline stimulated 2-deoxyglucose uptake; at higher concentrations adrenaline inhibited the uptake. In the presence of insulin at the maximum effective concentration, addition of adrenaline further increased the 2-deoxyglucose uptake by about 50%. In the presence of insulin 8-bromo-cAMP had the same effect as adrenaline. In the absence of insulin, 8-bromo-cAMP only inhibited 2-deoxyglucose uptake.
Collapse
|
28
|
Pfeifle J, Anderer FA. Isolation and localization of phosphoprotein pp 135 in the nucleoli of various cell lines. EUROPEAN JOURNAL OF BIOCHEMISTRY 1984; 139:417-24. [PMID: 6365552 DOI: 10.1111/j.1432-1033.1984.tb08021.x] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Phosphoprotein pp 135 is one of the dominant proteins endogenously phosphorylated in cellular sonicates during short-time exposure to [gamma-32P]ATP. Mouse cells growing exponentially show the highest pp 135 level as determined by endogenous phosphorylation and immunobinding assays. Disruption of cells in the absence of calcium at low magnesium concentration renders more than 90% pp 135 into the cytosolic fraction. A five-step purification yields greater than 95% pure pp 135. The cellular location of pp 135 was determined with a rat anti-(mouse pp 135) serum by immunofluorescence in mouse cell lines and cryostat sections of normal mouse tissue. We observed fluorescence predominantly of nucleolar structures, confirmed by studies of isolated nuclei and nucleoli. Cross-reacting nucleolar phosphoproteins were identified in cell lines of other species with molecular masses of 128 kDa (human), 135 kDa (hamster) and 118 kDa (Drosophila). Endogenous phosphorylation of pp 135 investigated with purified mouse nucleoli showed optimal activity at isotonicity, pH 7.3, in the presence of 10 mM magnesium ions.
Collapse
|
29
|
Kitagawa T, Akamatsu Y. Modulation of passive permeability by external ATP and cytoskeleton-attacking agents in cultured mammalian cells. BIOCHIMICA ET BIOPHYSICA ACTA 1983; 734:25-32. [PMID: 6615827 DOI: 10.1016/0005-2736(83)90070-6] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
External ATP causes a passive permeability change in several transformed cells, but not in untransformed cells. We previously demonstrated that in CHO-K1 cells, a transformed clone of Chinese hamster ovary cells, the external ATP-dependent permeability change was induced when the intracellular ATP concentration was reduced by a mitochondrial inhibitor (Kitagawa, T. and Akamatsu, Y. (1981) Biochim. Biophys. Acta 649, 76-82). A permeability change with similar characteristics was also observed when the CHO cells were treated with external ATP and a cytoskeleton-attacking agent such as vinblastine or cytochalasin B. Just like mitochondrial inhibitors, vinblastine could increase the sensitivity of transformed 3T3 cells to external ATP but showed no effect on passive permeability of normal 3T3 cells. However, in contrast with the effect of the mitochondrial inhibitors, the cytoskeleton drugs caused the permeability change with little reduction of intracellular ATP concentration, suggesting different actions of these two kinds of drug on the permeability change. The present results suggest an important role of cytoskeletal structures in controlling the external ATP-dependent permeability change in transformed cells. Possible effects of intracellular ATP on cytoskeletal structures are also discussed.
Collapse
|
30
|
May JM, Mikulecky DC. Glucose utilization in rat adipocytes. The interaction of transport and metabolism as affected by insulin. J Biol Chem 1983. [DOI: 10.1016/s0021-9258(18)32491-8] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
|
31
|
Krell H, Ermisch N, Kasperek S, Pfaff E. On the mechanisms of ATP-induced and succinate-induced redistribution of cations in isolated rat liver cells. EUROPEAN JOURNAL OF BIOCHEMISTRY 1983; 131:247-54. [PMID: 6832149 DOI: 10.1111/j.1432-1033.1983.tb07256.x] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
1. The ability of external ATP to induce calcium uptake in isolated rat liver cells was further characterized. Stimulation of calcium uptake was specific for ATP, other nucleotides or ATP metabolites had no comparable effect. ATP was dephosphorylated while stimulating calcium uptake, but there was no stoichiometry between ATP hydrolysis and calcium uptake nor did dephosphorylation depend on calcium concentration. ATP acted from outside and was dephosphorylated by an ecto-ATPase of the cells. 2. In addition to its direct action, ATP enhanced succinate-dependent calcium uptake in a cooperative fashion. This is best explained by different sites of action. ATP increases cell membrane permeability while succinate stimulates uptake into mitochondria. 3. ATP was able to lower Na+ and K+ gradients and the pH gradient between cells and incubation medium. Increasing calcium concentration counteracted this effect though calcium uptake was then stimulated. 4. Succinate alone did not affect monovalent cation gradients but raised the pH gradient. It partially counteracted the ATP effects on these gradients. 5. Since catecholamine-like actions of ATP may be mediated by an increase in cytoplasmic calcium concentration, the action of extracellular ATP can be taken as a model to study the role of calcium as a transmitter of hormone actions. From interdependence between ATP-stimulated and succinate-stimulated calcium uptake, conclusions can be drawn on the resulting cytoplasmic calcium concentration and its effect on plasma membrane permeability.
Collapse
|
32
|
Pfeifle J, Anderer FA. Isolation and characterization of phosphoprotein pp 105 from simian virus 40-transformed mouse fibroblasts. BIOCHIMICA ET BIOPHYSICA ACTA 1983; 762:86-93. [PMID: 6299384 DOI: 10.1016/0167-4889(83)90120-9] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Investigation of the cellular distribution of a 105 kDa phosphoprotein (pp 105) in transformed mouse fibroblasts, showed that only a minor amount was located on the surface of logarithmically grown suspension cells. More than 90% of total pp 105 was contained in the cytosolic fraction representing about 0.2% of total cytosolic proteins. Surface and cytosolic pp 105 had identical phosphopeptide patterns. Cytosolic pp 105 was highly purified by ammonium sulfate precipitation followed by three chromatographic steps and gel electrophoresis. The purified pp 105 was capable of weak autophosphorylation. In the stationary growth phase of suspension cells, the amount of pp 105 detectable by endogenous phosphorylation was only 10-15% of that observed during logarithmic growth. pp 105 was also detected in normal mouse tissue and its distribution determined.
Collapse
|
33
|
Stimulation of maximal intracellular insulin action on glycogen synthase by preincubation of adipocytes with adenosine 5'-triphosphate. J Biol Chem 1983. [DOI: 10.1016/s0021-9258(18)33107-7] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
|
34
|
May JM. The inhibition of hexose transport and metabolism by small amounts of adenosine 5'-triphosphate in isolated rat adipocytes. Arch Biochem Biophys 1982; 214:56-66. [PMID: 7044317 DOI: 10.1016/0003-9861(82)90008-x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
|
35
|
|
36
|
Pfeifle J, Hagmann W, Anderer FA. Cell adhesion-dependent differences in endogenous protein phosphorylation on the surface of various cell lines. BIOCHIMICA ET BIOPHYSICA ACTA 1981; 670:274-84. [PMID: 6271243 DOI: 10.1016/0005-2795(81)90020-9] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Endogenous phosphorylation of intact cells was studied with four mouse, hamster and human cell lines using [gamma-32P]ATP and [gamma-32P]GTP as exogenous substrates. With all four cell lines distinct differences in the phosphoprotein patterns could be demonstrated for cells grown in suspension culture compared to cells grown in monolayers. Two major, apparently ubiquitous phosphoproteins with molecular weights of 135 000 (128 000 in HeLa cells) and 105 000, representing up to 60% of total phosphorylation, were phosphorylated only in cells grown in suspension. These phosphoproteins and the kinase(s) were located on the surface of the suspension cells. Evidence showed that phosphorylation was apparently not a true endogenous reaction, that rather it occurred by cell-cell collision, showing exponentially increasing 32P incorporation with increasing cell population density. Phosphorylation of pp135 and pp105 was established with ATP as well as with GTP and was not dependent on cyclic nucleotides cyclic AMP, cyclic GMP and cyclic CMP. The substrate-attached cells of all four cell lines have protein kinases on the cell surface. The lack of pp135 and pp105 phosphorylation may be due to the fact that these phosphoproteins are not expressed at all on the surface of substrate-attached cells or that these phosphoproteins are already fully phosphorylated.
Collapse
|
37
|
Abstract
An ecto-adenosine triphosphatase (E.C. 3.6.1.4 ATP-phosphohydrolase) is shown to be localized on the outer surface of varieties of cell membrane. The enzyme is different from the ATPase involved in biological energy transduction and ion transport mechanism. The characteristic of the enzyme lies in having a very broad substrate specificity and is inhibited by EDTA and higher concentration of ATP. The enzyme is dependent on bivalent metal ions, Mg++ or Ca++ for its optimum activity. The enzyme is highly sensitive to SH-reagents but insensitive to inhibitors of mitochondrial ATPase or Na+- K+- ATPase. The possible functions of the enzyme in being oriented outside the cell membrane is discussed.
Collapse
|
38
|
Role of fatty acid synthesis in the control of insulin-stimulated glucose utilization by rat adipocytes. J Lipid Res 1981. [DOI: 10.1016/s0022-2275(20)37346-6] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
|
39
|
Scott RE, Boman BM, Swartzendruber DE, Zschunke MA, Hoerl BJ. Cell cycle-associated modulation in cAMP-dependent plasma membrane phosphorylation. Exp Cell Res 1981; 133:73-82. [PMID: 6263655 DOI: 10.1016/0014-4827(81)90358-x] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
|
40
|
Kaplan ML, Leveille GA. Development of lipogenesis and insulin sensitivity in tissues of the ob/ob mouse. THE AMERICAN JOURNAL OF PHYSIOLOGY 1981; 240:E101-7. [PMID: 6781359 DOI: 10.1152/ajpendo.1981.240.2.e101] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
Lipogenesis and insulin sensitivity are evaluated in adipose tissue, liver, and diaphragm of ob/ob and non-ob/ob mice. In ob/ob mice, hepatic fatty acid synthesis from [U-14C]glucose is elevated by 4 wk of age, and adipose tissue fatty acid synthesis increases at approximately 7 wk. Hepatic activities in ob/ob mice of glucose-6-phosphate dehydrogenase (EC 1.1.1.49), 6-phosphogluconate dehydrogenase (EC 1.1.1.44), malate dehydrogenase (EC 1.1.1.40), and alpha-glycerophosphate dehydrogenase (EC 1.1.1.8) are dramatically increased by 7 wk of age. Diminished insulin-stimulated glycogen synthesis is first noted in the diaphragm of ob/ob mice at 7 wk of age. Insulin-stimulated glycogen synthesis in adipose tissue of ob/ob mice is impaired at 3 wk. At 7 wk, insulin-stimulated fatty acid synthesis in adipose tissue of ob/ob mice is markedly increased. Adipose tissue glyceride-glycerol synthesis continues to increase throughout development, whereas fatty acid synthesis decreases after 7 wk. The data suggest that alterations in lipid synthesis occur very early in the development of ob/ob mouse, prior to expression to overt obesity, at which time a major contribution to lipogenesis is made by the liver. The altered de novo lipogenesis does not precede the reported diminution in energy metabolism.
Collapse
|
41
|
Shechter Y, Sela BA. Insulin-like effects of wax bean agglutinin in rat adipocytes. Biochem Biophys Res Commun 1981; 98:367-73. [PMID: 6261737 DOI: 10.1016/0006-291x(81)90849-4] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
|
42
|
Ronquist G, Agren G, Nilsson K. Autophosphorylation at the outer surface of different human cells in culture. Ups J Med Sci 1981; 86:137-42. [PMID: 6459669 DOI: 10.3109/03009738109179221] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
|
43
|
Makan NR. Passive membrane permeability to small molecules and ions in transformed mammalian cells: probable role of surface phosphorylation. J Cell Physiol 1981; 106:49-61. [PMID: 6259185 DOI: 10.1002/jcp.1041060107] [Citation(s) in RCA: 27] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Addition of ATP to medium surrounding intact, transformed 3T3 cells causes the formation of aqueous channels in the plasma membrane. This effect of extracellular ATP is sharply dependent on the pH and temperature of the incubation medium, and is inhibited by low levels of La3+ or ruthenium red; inhibition is also obtained with concentrations of Mg2+ ions that exceed a ratio of Mg/ATP of one. The effect of ATP on membrane channel formation is unaffected by chelators of metal ions or by prior modification of the cell surface with various surface-active enzymes or sulfhydryl reagents. Under conditions which favor aqueous channel formation, incubation of intact 3T6 cells with ATP (gamma-32P) leads to phosphorylation of two membrane components with apparent molecular weight of 40,000 (40K) and 110,000 (110K) daltons; the 110K component which is unaffected by trypsin under normal conditions is rendered trypsin-sensitive by the phosphorylation reaction, probably as a result of a conformational change. Conditions which inhibit aqueous channel formation also inhibit phosphorylation of the 110K protein and decrease the labeling of the 40K component. These results indicate the probable role of cell surface phosphorylation, involving one or both of these components, in the formation of aqueous channels in transformed 3T3 cells. Aqueous channel formation by extracellular ATP is not associated with gross unfolding of the cell surface as revealed by lactoperoxidase-catalyzed iodination of the 3T6 cell surface.
Collapse
|
44
|
Hilf R, Sorge LK, Gay RJ. Insulin binding and glucose transport. INTERNATIONAL REVIEW OF CYTOLOGY 1981; 72:147-202. [PMID: 7019131 DOI: 10.1016/s0074-7696(08)61196-1] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
|
45
|
|
46
|
Role of ATP in specific binding of125I-insulin with cytoplasmic receptors of liver and muscle membranes of control animals and of rats with diabetes. Bull Exp Biol Med 1980. [DOI: 10.1007/bf00834085] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
|
47
|
Vega FV, Key RJ, Jordan JE, Kono T. Reversal of insulin effects in fat cells may require energy for deactivation of glucose transport, but not deactivation of phosphodiesterase. Arch Biochem Biophys 1980; 203:167-73. [PMID: 6157364 DOI: 10.1016/0003-9861(80)90165-4] [Citation(s) in RCA: 35] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
|
48
|
Shechter Y, Karlish SJ. Insulin-like stimulation of glucose oxidation in rat adipocytes by vanadyl (IV) ions. Nature 1980; 284:556-8. [PMID: 6988725 DOI: 10.1038/284556a0] [Citation(s) in RCA: 429] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
|
49
|
Lever JE. The use of membrane vesicles in transport studies. CRC CRITICAL REVIEWS IN BIOCHEMISTRY 1980; 7:187-246. [PMID: 6243082 DOI: 10.3109/10409238009105462] [Citation(s) in RCA: 61] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Transport-competent plasma membrane vesicles isolated from mammalian cells provide a system to investigate mechanisms and regulation of nutrient and ion transport systems. The characteristics of membrane vesicle systems to study transport in erythrocytes, renal and epithelial membranes, Ehrlich ascites cells, and mouse fibroblasts are discussed. Studies of Na+-stimulated and Na+-independent amino acid and glucose transport in these systems are evaluated, with emphasis on experimental verification of concepts stated in the Na+ gradient hypothesis. Nucleoside, phosphate, and calcium transport systems in plasma membrane vesicles from mouse fibroblast cultures are discussed. Also, current biochemical approaches to investigate mechanisms of regulation of nutrient transport systems by hormones or cellular proliferative state are described.
Collapse
|
50
|
Garratt CJ, Hubbard RE, Ponnudurai TB. Adipose tissue, obesity and insulin. PROGRESS IN MEDICINAL CHEMISTRY 1980; 17:105-49. [PMID: 7031767 DOI: 10.1016/s0079-6468(08)70158-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
|