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Murakami K, Furuya H, Hokutan K, Goodison S, Pagano I, Chen R, Shen CH, Chan MWY, Ng CF, Kobayashi T, Ogawa O, Miyake M, Thornquist M, Shimizu Y, Hayashi K, Wang Z, Yu H, Rosser CJ. Association of SNPs in the PAI1 Gene with Disease Recurrence and Clinical Outcome in Bladder Cancer. Int J Mol Sci 2023; 24:4943. [PMID: 36902377 PMCID: PMC10003630 DOI: 10.3390/ijms24054943] [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: 02/08/2023] [Revised: 02/28/2023] [Accepted: 03/02/2023] [Indexed: 03/08/2023] Open
Abstract
PURPOSE Bladder cancer (BCa) is one of the most common cancer types worldwide and is characterized by a high rate of recurrence. In previous studies, we and others have described the functional influence of plasminogen activator inhibitor-1 (PAI1) in bladder cancer development. While polymorphisms in PAI1 have been associated with increased risk and worsened prognosis in some cancers, the mutational status of PAI1 in human bladder tumors has not been well defined. METHODS In this study, we evaluated the mutational status of PAI1 in a series of independent cohorts, comprised of a total of 660 subjects. RESULTS Sequencing analyses identified two clinically relevant 3' untranslated region (UTR) single nucleotide polymorphisms (SNPs) in PAI1 (rs7242; rs1050813). Somatic SNP rs7242 was present in human BCa cohorts (overall incidence of 72%; 62% in Caucasians and 72% in Asians). In contrast, the overall incidence of germline SNP rs1050813 was 18% (39% in Caucasians and 6% in Asians). Furthermore, Caucasian patients with at least one of the described SNPs had worse recurrence-free survival and overall survival (p = 0.03 and p = 0.03, respectively). In vitro functional studies demonstrated that SNP rs7242 increased the anti-apoptotic effect of PAI1, and SNP rs1050813 was related to a loss of contact inhibition associated with cellular proliferation when compared to wild type. CONCLUSION Further investigation of the prevalence and potential downstream influence of these SNPs in bladder cancer is warranted.
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Affiliation(s)
- Kaoru Murakami
- Samuel Oschin Comprehensive Cancer Institute, Cedars-Sinai Medical Center, Los Angeles, CA 90048, USA
| | - Hideki Furuya
- Samuel Oschin Comprehensive Cancer Institute, Cedars-Sinai Medical Center, Los Angeles, CA 90048, USA
| | - Kanani Hokutan
- Clinical and Translational Research Program, University of Hawaii Cancer Center, Honolulu, HI 96813, USA
- Department of Molecular Biosciences and Bioengineering, University of Hawaii at Manoa, Honolulu, HI 96822, USA
| | - Steve Goodison
- Department of Quantitative Health Sciences, Mayo Clinic, Jacksonville, FL 32224, USA
| | - Ian Pagano
- Population Sciences in the Pacific Program, University of Hawaii Cancer Center, Honolulu, HI 96813, USA
| | - Runpu Chen
- Department of Microbiology and Immunology, The State University of New York at Buffalo, Buffalo, NY 14260, USA
| | - Cheng-Huang Shen
- Department of Urology, Ditmanson Medical Foundation Chia-Yi Christian Hospital, Chiayi 600, Taiwan
| | - Michael W. Y. Chan
- Department of Biomedical Sciences, National Chung Cheng University, Chia-Yi 621, Taiwan
| | - Chi Fai Ng
- SH Ho Urology Centre, Department of Surgery, The Chinese University of Hong Kong, Hong Kong
| | - Takashi Kobayashi
- Department of Urology, Kyoto University Graduate School of Medicine, Kyoto 606-8507, Japan
| | - Osamu Ogawa
- Department of Urology, Kyoto University Graduate School of Medicine, Kyoto 606-8507, Japan
| | - Makito Miyake
- Department of Urology, Nara Medical University, Nara 6348522, Japan
| | - Mark Thornquist
- Fred Hutchinson Cancer Research Center, Seattle, WA 98109, USA
| | - Yoshiko Shimizu
- Clinical and Translational Research Program, University of Hawaii Cancer Center, Honolulu, HI 96813, USA
- Department of Molecular Biosciences and Bioengineering, University of Hawaii at Manoa, Honolulu, HI 96822, USA
| | - Kazukuni Hayashi
- Clinical and Translational Research Program, University of Hawaii Cancer Center, Honolulu, HI 96813, USA
| | - Zhangwei Wang
- Population Sciences in the Pacific Program, University of Hawaii Cancer Center, Honolulu, HI 96813, USA
| | - Herbert Yu
- Population Sciences in the Pacific Program, University of Hawaii Cancer Center, Honolulu, HI 96813, USA
| | - Charles J. Rosser
- Samuel Oschin Comprehensive Cancer Institute, Cedars-Sinai Medical Center, Los Angeles, CA 90048, USA
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Petersen MC, Shulman GI. Mechanisms of Insulin Action and Insulin Resistance. Physiol Rev 2018; 98:2133-2223. [PMID: 30067154 PMCID: PMC6170977 DOI: 10.1152/physrev.00063.2017] [Citation(s) in RCA: 1400] [Impact Index Per Article: 233.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2017] [Revised: 03/22/2018] [Accepted: 03/24/2018] [Indexed: 12/15/2022] Open
Abstract
The 1921 discovery of insulin was a Big Bang from which a vast and expanding universe of research into insulin action and resistance has issued. In the intervening century, some discoveries have matured, coalescing into solid and fertile ground for clinical application; others remain incompletely investigated and scientifically controversial. Here, we attempt to synthesize this work to guide further mechanistic investigation and to inform the development of novel therapies for type 2 diabetes (T2D). The rational development of such therapies necessitates detailed knowledge of one of the key pathophysiological processes involved in T2D: insulin resistance. Understanding insulin resistance, in turn, requires knowledge of normal insulin action. In this review, both the physiology of insulin action and the pathophysiology of insulin resistance are described, focusing on three key insulin target tissues: skeletal muscle, liver, and white adipose tissue. We aim to develop an integrated physiological perspective, placing the intricate signaling effectors that carry out the cell-autonomous response to insulin in the context of the tissue-specific functions that generate the coordinated organismal response. First, in section II, the effectors and effects of direct, cell-autonomous insulin action in muscle, liver, and white adipose tissue are reviewed, beginning at the insulin receptor and working downstream. Section III considers the critical and underappreciated role of tissue crosstalk in whole body insulin action, especially the essential interaction between adipose lipolysis and hepatic gluconeogenesis. The pathophysiology of insulin resistance is then described in section IV. Special attention is given to which signaling pathways and functions become insulin resistant in the setting of chronic overnutrition, and an alternative explanation for the phenomenon of ‟selective hepatic insulin resistanceˮ is presented. Sections V, VI, and VII critically examine the evidence for and against several putative mediators of insulin resistance. Section V reviews work linking the bioactive lipids diacylglycerol, ceramide, and acylcarnitine to insulin resistance; section VI considers the impact of nutrient stresses in the endoplasmic reticulum and mitochondria on insulin resistance; and section VII discusses non-cell autonomous factors proposed to induce insulin resistance, including inflammatory mediators, branched-chain amino acids, adipokines, and hepatokines. Finally, in section VIII, we propose an integrated model of insulin resistance that links these mediators to final common pathways of metabolite-driven gluconeogenesis and ectopic lipid accumulation.
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Affiliation(s)
- Max C Petersen
- Departments of Internal Medicine and Cellular & Molecular Physiology, Howard Hughes Medical Institute, Yale University School of Medicine , New Haven, Connecticut
| | - Gerald I Shulman
- Departments of Internal Medicine and Cellular & Molecular Physiology, Howard Hughes Medical Institute, Yale University School of Medicine , New Haven, Connecticut
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Marques F, Crespo ME, Pantaleão O, Bicho M. Insulin activation of NADH ferricyanide reductase in human erythrocytes is mediated by the insulin receptor tyrosine kinase: a comparative study in normal and diabetic states. Redox Rep 2016; 2:373-8. [DOI: 10.1080/13510002.1996.11747077] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022] Open
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Cinar R, Godlewski G, Liu J, Tam J, Jourdan T, Mukhopadhyay B, Harvey-White J, Kunos G. Hepatic cannabinoid-1 receptors mediate diet-induced insulin resistance by increasing de novo synthesis of long-chain ceramides. Hepatology 2014; 59:143-53. [PMID: 23832510 PMCID: PMC3839256 DOI: 10.1002/hep.26606] [Citation(s) in RCA: 127] [Impact Index Per Article: 12.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/17/2013] [Accepted: 06/20/2013] [Indexed: 12/14/2022]
Abstract
UNLABELLED Obesity is associated with increased activity of two lipid signaling systems (endocannabinoids [ECs] and ceramides), with both being implicated in insulin resistance. Cannabinoid-1 receptor (CB1 R) antagonists reverse obesity and insulin resistance, but have psychiatric side effects. Here we analyzed the role of ceramide in CB1 R-mediated insulin resistance in C57Bl6/J mice with high-fat diet-induced obesity (DIO), using JD5037, a peripherally restricted CB1 R inverse agonist. Chronic JD5037 treatment of DIO mice reduced body weight and steatosis and improved glucose tolerance and insulin sensitivity. Peripheral CB1 R blockade also attenuated the diet-induced increase in C14:0, C16:0, C18:0, and C20:0 ceramide species with either C16 or C18 sphingosine-base in the liver. Decreased ceramide levels reflected their reduced de novo synthesis, due to inhibition of the activity of serine-palmitoyl transferase (SPT) and the expression of its SPTLC3 catalytic subunit, as well as reduced ceramide synthase (CerS) activity related to reduced expression of CerS1 and CerS6. JD5037 treatment also increased ceramide degradation due to increased expression of ceramidases. In primary cultured mouse hepatocytes and HepG2 cells, the EC anandamide increased ceramide synthesis in an eIF2α-dependent manner, and inhibited insulin-induced akt phosphorylation by increased serine phosphorylation of IRS1 and increased expression of the serine/threonine phosphatase Phlpp1. These effects were abrogated by JD5037 or the SPT inhibitor myriocin. Chronic treatment of DIO mice with myriocin or JD5037 similarly reversed hepatic insulin resistance, as verified using a euglycemic/hyperinsulinemic clamp. CONCLUSION ECs induce CB1 R-mediated, endoplasmic reticulum stress-dependent synthesis of specific ceramide subspecies in the liver, which plays a key role in obesity-related hepatic insulin resistance.
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Affiliation(s)
- Resat Cinar
- Laboratory of Physiological Studies; National Institute on Alcohol Abuse and Alcoholism; National Institutes of Health; Bethesda MD
| | - Grzegorz Godlewski
- Laboratory of Physiological Studies; National Institute on Alcohol Abuse and Alcoholism; National Institutes of Health; Bethesda MD
| | - Jie Liu
- Laboratory of Physiological Studies; National Institute on Alcohol Abuse and Alcoholism; National Institutes of Health; Bethesda MD
| | - Joseph Tam
- Laboratory of Physiological Studies; National Institute on Alcohol Abuse and Alcoholism; National Institutes of Health; Bethesda MD
| | - Tony Jourdan
- Laboratory of Physiological Studies; National Institute on Alcohol Abuse and Alcoholism; National Institutes of Health; Bethesda MD
| | - Bani Mukhopadhyay
- Laboratory of Physiological Studies; National Institute on Alcohol Abuse and Alcoholism; National Institutes of Health; Bethesda MD
| | - Judith Harvey-White
- Laboratory of Physiological Studies; National Institute on Alcohol Abuse and Alcoholism; National Institutes of Health; Bethesda MD
| | - George Kunos
- Laboratory of Physiological Studies; National Institute on Alcohol Abuse and Alcoholism; National Institutes of Health; Bethesda MD
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Summermatter S, Shui G, Maag D, Santos G, Wenk MR, Handschin C. PGC-1α improves glucose homeostasis in skeletal muscle in an activity-dependent manner. Diabetes 2013; 62:85-95. [PMID: 23086035 PMCID: PMC3526021 DOI: 10.2337/db12-0291] [Citation(s) in RCA: 74] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
Metabolic disorders are a major burden for public health systems globally. Regular exercise improves metabolic health. Pharmacological targeting of exercise mediators might facilitate physical activity or amplify the effects of exercise. The peroxisome proliferator-activated receptor γ coactivator 1α (PGC-1α) largely mediates musculoskeletal adaptations to exercise, including lipid refueling, and thus constitutes such a putative target. Paradoxically, forced expression of PGC-1α in muscle promotes diet-induced insulin resistance in sedentary animals. We show that elevated PGC-1α in combination with exercise preferentially improves glucose homeostasis, increases Krebs cycle activity, and reduces the levels of acylcarnitines and sphingosine. Moreover, patterns of lipid partitioning are altered in favor of enhanced insulin sensitivity in response to combined PGC-1α and exercise. Our findings reveal how physical activity improves glucose homeostasis. Furthermore, our data suggest that the combination of elevated muscle PGC-1α and exercise constitutes a promising approach for the treatment of metabolic disorders.
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Affiliation(s)
- Serge Summermatter
- Biozentrum, Division of Pharmacology/Neurobiology, University of Basel, Basel, Switzerland
| | - Guanghou Shui
- Department of Biochemistry, Yong Loo Lin School of Medicine, National University of Singapore, Singapore
| | - Daniela Maag
- Division of Clinical Chemistry and Biochemistry, Department of Pediatrics, University Children’s Hospital, University of Zurich, Zurich, Switzerland
| | - Gesa Santos
- Biozentrum, Division of Pharmacology/Neurobiology, University of Basel, Basel, Switzerland
| | - Markus R. Wenk
- Department of Biochemistry, Yong Loo Lin School of Medicine, National University of Singapore, Singapore
- Swiss Tropical and Public Health Institute, Basel, Switzerland
| | - Christoph Handschin
- Biozentrum, Division of Pharmacology/Neurobiology, University of Basel, Basel, Switzerland
- Corresponding author: Christoph Handschin,
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Longato L, Tong M, Wands JR, de la Monte SM. High fat diet induced hepatic steatosis and insulin resistance: Role of dysregulated ceramide metabolism. Hepatol Res 2012; 42:412-27. [PMID: 22176347 PMCID: PMC4096625 DOI: 10.1111/j.1872-034x.2011.00934.x] [Citation(s) in RCA: 81] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
AIM Non-alcoholic fatty liver disease (NAFLD) is an insulin resistance disease that can progress to cirrhosis and liver failure. We hypothesized that in NAFLD, insulin resistance dysregulates lipid metabolism, increasing production of cytotoxic lipids including ceramides, which exacerbate hepatic insulin resistance and injury. METHODS Long Evans rats were pair-fed low (LFD) or high (HFD) fat diets for 8 weeks. Livers were used to measure lipids, gene expression, insulin receptor binding, integrity of insulin signaling, and pro-inflammatory cytokines. In vitro experiments characterized effects of ceramides on Huh7 cell viability, mitochondrial function, and insulin signaling. RESULTS High fat diet feeding caused NAFLD with peripheral and hepatic insulin resistance, increased hepatic expression of pro-ceramide genes, sphingomyelinase activity, and lipid peroxidation, and increased serum ceramide. Ceramide treatment impaired Huh7 cell viability, mitochondrial function, and insulin signaling. CONCLUSIONS Increased hepatic ceramide generation and release may mediate both hepatic and peripheral insulin resistance in NAFLD.
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Affiliation(s)
- Lisa Longato
- Departments of Medicine, Pathology and Neurology, Divisions of Gastroenterology and Neuropathology, and the Liver Research Center, Rhode Island Hospital and the Warren Alpert Medical School of Brown University, Providence, RI, USA
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Chavez JA, Holland WL, Bär J, Sandhoff K, Summers SA. Acid ceramidase overexpression prevents the inhibitory effects of saturated fatty acids on insulin signaling. J Biol Chem 2005; 280:20148-53. [PMID: 15774472 DOI: 10.1074/jbc.m412769200] [Citation(s) in RCA: 165] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
Recent studies indicate that insulin resistance and type 2 diabetes result from the accumulation of lipids in tissues not suited for fat storage, such as skeletal muscle and the liver. To elucidate the mechanisms linking exogenous fats to the inhibition of insulin action, we evaluated the effects of free fatty acids (FFAs) on insulin signal transduction in cultured C2C12 myotubes. As we described previously (Chavez, J. A., and Summers, S. A. (2003) Arch. Biochem. Biophys. 419, 101-109), long-chain saturated FFAs inhibited insulin stimulation of Akt/protein kinase B, a central regulator of glucose uptake and anabolic metabolism. Moreover, these FFAs stimulated the de novo synthesis of ceramide and sphingosine, two sphingolipids shown previously to inhibit insulin action. To determine the contribution of either sphingolipid in FFA-dependent inhibition of insulin action, we generated C2C12 myotubes that constitutively overexpress acid ceramidase (AC), an enzyme that catalyzes the lysosomal conversion of ceramide to sphingosine. AC overexpression negated the inhibitory effects of saturated FFAs on insulin signaling while blocking their stimulation of ceramide accumulation. By contrast, AC overexpression stimulated the accrual of sphingosine. These results support a role for aberrant accumulation of ceramide, but not sphingosine, in the inhibition of muscle insulin sensitivity by exogenous FFAs.
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Affiliation(s)
- Jose Antonio Chavez
- Department of Internal Medicine, Division of Endocrinology, Metabolism, and Diabetes, University of Utah, Salt Lake City, 84132, USA
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8
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Vesper H, Schmelz EM, Nikolova-Karakashian MN, Dillehay DL, Lynch DV, Merrill AH. Sphingolipids in food and the emerging importance of sphingolipids to nutrition. J Nutr 1999; 129:1239-50. [PMID: 10395583 DOI: 10.1093/jn/129.7.1239] [Citation(s) in RCA: 371] [Impact Index Per Article: 14.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Eukaryotic organisms as well as some prokaryotes and viruses contain sphingolipids, which are defined by a common structural feature, i.e. , a "sphingoid base" backbone such as D-erythro-1,3-dihydroxy, 2-aminooctadec-4-ene (sphingosine). The sphingolipids of mammalian tissues, lipoproteins, and milk include ceramides, sphingomyelins, cerebrosides, gangliosides and sulfatides; plants, fungi and yeast have mainly cerebrosides and phosphoinositides. The total amounts of sphingolipids in food vary considerably, from a few micromoles per kilogram (fruits) to several millimoles per kilogram in rich sources such as dairy products, eggs and soybeans. With the use of the limited data available, per capita sphingolipid consumption in the United States can be estimated to be on the order of 150-180 mmol (approximately 115-140 g) per year, or 0.3-0.4 g/d. There is no known nutritional requirement for sphingolipids; nonetheless, they are hydrolyzed throughout the gastrointestinal tract to the same categories of metabolites (ceramides and sphingoid bases) that are used by cells to regulate growth, differentiation, apoptosis and other cellular functions. Studies with experimental animals have shown that feeding sphingolipids inhibits colon carcinogenesis, reduces serum LDL cholesterol and elevates HDL, suggesting that sphingolipids represent a "functional" constituent of food. Sphingolipid metabolism can also be modified by constituents of the diet, such as cholesterol, fatty acids and mycotoxins (fumonisins), with consequences for cell regulation and disease. Additional associations among diet, sphingolipids and health are certain to emerge as more is learned about these compounds.
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Affiliation(s)
- H Vesper
- Departments of Biochemistry and Pathology, and Division of Animal Resources, Emory University, Atlanta, GA 30322-3050, USA
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Miura A, Ishizuka T, Kanoh Y, Ishizawa M, Itaya S, Kimura M, Kajita K, Yasuda K. Effect of tumor necrosis factor-alpha on insulin signal transduction in rat adipocytes: relation to PKCbeta and zeta translocation. BIOCHIMICA ET BIOPHYSICA ACTA 1999; 1449:227-38. [PMID: 10209302 DOI: 10.1016/s0167-4889(99)00016-6] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Although much evidence has been accumulated suggesting that tumor necrosis factor-alpha (TNF-alpha) is an important mediator of insulin resistance, the precise mechanism involved is still unclear. Recently, it has been reported that insulin-induced glucose uptake is mediated by activation of second messengers such as insulin receptor substrate 1 (IRS-1), phosphatidylinositol 3-kinase (PI3K), and diacylglycerol (DG)-protein kinase C (PKC). We have examined the effect of TNF-alpha on insulin-induced glucose uptake and activations of tyrosine kinase, IRS-1, PI3K and PKC in rat adipocytes. Pretreatment with 0.1-100 nM TNF-alpha for 60 min resulted in a significant decrease in 10 nM insulin- or 1 microM 12-O-tetradecanoyl phorbol-13-acetate (TPA)-induced [3H]2-deoxyglucose uptake without affecting basal glucose uptake. 10 nM insulin-stimulated activation of tyrosine kinase, IRS-1 and PI3K was suppressed by preincubation with 0.1-10 nM TNF-alpha for 60 min. 10 nM TNF-alpha pretreatment also suppressed 10 nM insulin- and 1 microM TPA-induced increases in membrane-associated PKCbeta and PKCzeta. Furthermore, 10 nM TNF-alpha, by itself, altered PKCbeta translocation from the membrane to cytosol. These results suggest that TNF-alpha inhibits insulin-stimulated activation of both the tyrosine kinase-IRS-1-PI3K-PKCzeta pathway and DG-PKC pathway. Finally, TNF-alpha contributes to insulin resistance in rat adipocytes.
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Affiliation(s)
- A Miura
- The Third Department of Internal Medicine, Gifu University School of Medicine, Gifu 500-8705, Japan
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10
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Riboni L, Bassi R, Caminiti A, Prinetti A, Viani P, Tettamanti G. Metabolic fate of exogenous sphingosine in neuroblastoma neuro2A cells. Dose-dependence and biological effects. Ann N Y Acad Sci 1998; 845:46-56. [PMID: 9668342 DOI: 10.1111/j.1749-6632.1998.tb09661.x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The possible relationship between metabolism and biological effects of sphingosine was investigated in Neuro2a cells. [C3-3H]-sphingosine, administered at different doses (80 pmol-80 nmol/mg cell protein). Amounts up to hundredfold were rapidly taken up and metabolized, the intracellular content of sphingosine being processed within 2 h. At low doses, [3H]-sphingosine represented a minor portion of the cellular radiolabel, and N-acylated metabolites, particularly ceramide, prevailed over degradation products. Neuro2a cell differentiation took place in conjunction with ceramide increase. At increasing exogenous sphingosine/cell ratio, the acylation process became saturated while sphingosine degradation increased proportionally. From this point on [3H]-sphingosine accumulated and cell toxicity occurred. In conclusion, in Neuro2a cells the biological effects exerted by exogenous sphingosine are strictly connected to the exogenous sphingosine/cell ratio and to the capacity of the cell to metabolize sphingosine.
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Affiliation(s)
- L Riboni
- Department of Medical Chemistry and Biochemistry, University of Milan, Italy
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11
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Walaas O, Horn RS, Walaas SI. The protein kinase C pseudosubstrate peptide (PKC19-36) inhibits insulin-stimulated protein kinase activity and insulin-mediated translocation of the glucose transporter glut 4 in streptolysin-O permeabilized adipocytes. FEBS Lett 1997; 413:152-6. [PMID: 9287134 DOI: 10.1016/s0014-5793(97)00898-3] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
The effect of insulin on protein kinase activity and plasma membrane translocation of the glucose transporter GLUT 4 has been studied in adipocytes permeabilized by Streptolysin-O. Insulin increased protein kinase activity, and this was completely inhibited by the PKC pseudosubstrate inhibitor peptide (PKC19-36). Insulin-mediated translocation of GLUT 4 was also inhibited by the PKC inhibitor peptide. Both these insulin effects were blocked by a PKCbeta neutralizing antibody. Our results are consistent with the hypothesis that insulin activates PKCbeta activity in adipocytes in situ, and that this PKC activation is a component of the system whereby insulin regulates translocation of GLUT 4 to the plasma membrane.
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Affiliation(s)
- O Walaas
- Neurochemical Laboratory, University of Oslo, Norway
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Abstract
We examined the effect of reducing ambient and intracellular free Mg ion ([Mg]i) concentrations on insulin action in epididymal adipocytes from male Sprague-Dawley rats in terms of (1) cellular transport of nonmetabolizable 2-deoxyglucose, (2) [U-14C]glucose oxidation to CO2, and (3) D-[3H]glucose incorporation into triglycerides. There were no significant differences in basal or insulin-stimulated transport of 2-deoxyglucose between adipocytes cultured in physiologic (1.24 mmol) or low (0.16 mmol) Mg for up to 24 hours. In contrast, insulin-stimulated but not basal [U-14C]glucose oxidation to CO2 was significantly reduced in adipocytes cultured in low versus physiologic Mg (P < .05 to .01). Similarly, there were no differences in basal glucose incorporation into triglycerides between cells cultured in low or physiologic Mg media for up to 24 hours. However, long-term (24-hour) but not short-term (2-hour) exposure of cells to low Mg was associated with a significant 30% reduction in insulin-stimulated D-[3H]glucose incorporation into triglycerides. When adipocytes incubated in low Mg were reincubated in high Mg (1.24 or 5 mmol) for 30 minutes, normal insulin-stimulated D-[3H]glucose incorporation into triglycerides was restored. Incubation of adipocytes in low Mg (0.16 mmol) for 24 hours resulted in a significant decrease in [Mg]i (264 +/- 89 v 437 +/- 125 micromol/cell [mean +/- SEM]) as compared with cells incubated in physiologic Mg (1.24 mmol; P < .01). These data support a role for intracellular Mg deficiency in the development of insulin resistance and suggest that the effect occurs at a site(s) distal to glucose entry into the cell. The effect of Mg deficiency on insulin action appears to be reversible.
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Affiliation(s)
- F R Kandeel
- Department of Diabetes, Endocrinology and Metabolism, City of Hope National Medical Center, Duarte, CA 91010, USA
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Ballou LR, Laulederkind SJ, Rosloniec EF, Raghow R. Ceramide signalling and the immune response. BIOCHIMICA ET BIOPHYSICA ACTA 1996; 1301:273-87. [PMID: 8664339 DOI: 10.1016/0005-2760(96)00004-5] [Citation(s) in RCA: 197] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Ceramide, produced through either the induction of SM hydrolysis or synthesized de novo transduces signals mediating differentiation, growth, growth arrest, apoptosis, cytokine biosynthesis and secretion, and a variety of other cellular functions. A generalized ceramide signal transduction scheme is shown in Fig. 2 in which ceramide is generated through the activation of distinct SMases residing in separate subcellular compartments in response to specific stimuli. Clearly, specificity of cellular responses to ceramide depends upon many factors which include the nature of the stimulus, co-stimulatory signals and the cell type involved. Ceramide derived from neutral SMase activation is thought to be involved in modulating CAPK and MAP kinases, PLA2 (arachidonic acid mobilization), and CAPP while ceramide generated through acid SMase activation appears to be primarily involved in NF-kappa B activation. While there is no apparent cross-talk between these two ceramide-mediated signalling pathways, there is likely to be significant cross-talk between ceramide signalling and other signal transduction pathways (e.g., the PKC and MAP kinase pathways). Other downstream targets for ceramide action include Cox, IL-6 and IL-2 gene expression, PKC zeta, Vav, Rb, c-Myc, c-Fos, c-Jun and other transcriptional regulators. Many, if not all, of these ceramide-mediated signalling events have been identified in the various cells comprising the immune system and are integral to the optimal functioning of the immune system. Although the role of the SM pathway and the generation of ceramide in T and B lymphocytes have only recently been recognized, it is clear from these studies that signal transduction through SM and ceramide can strongly affect the immune response, either directly through cell signalling events, or indirectly through cytokines produced by other cells as the result of signalling through the SM pathway. An overview of the signalling mechanisms coupling ceramide to the modulation of the immune response is depicted in Fig. 3 and shows how ceramide may play pivotal roles in regulating a number of complex processes. The SM pathway represents a potentially valuable focal point for therapeutic control of immune responses, perhaps for either enhancement of the activity of T cells in the elimination of tumors, or the down-regulation of lymphocyte function in instances of autoimmune disease. The recent explosion of knowledge regarding ceramide signalling notwithstanding, a number of critical questions need to be answered before a comprehensive, mechanistic understanding can be formulated relative to the incredibly varied effects of ceramide on cell function. For example, (i) how is a structurally simple molecule like ceramide able to mediate so many different, and sometimes paradoxical, physiological responses ranging from cell proliferation and differentiation to inhibition of cell growth and apoptosis, (ii) what are the molecular identities and modes of activation of the various SMase isoforms, (iii) what determines the distribution of the unique isoforms of SMase in cells of different lineages or at different stages of differentiation, (iv) what is the relative contribution of ceramide generated through SM hydrolysis versus de novo synthesis, and (v) by what means does ceramide interact with specific intracellular targets? Although a number of ceramide-activatable kinases, phosphatases, and their protein substrates have been identified, a more extensive search for additional cellular targets will be indispensable in determining the phosphorylation cascades linking the activation of the SM pathway to the regulation of nuclear events. Clearly, cross-talk between ceramide-induced signal transduction cascades and other signalling pathways adds to the inherent difficulty in distinguishing the specific effects of complex, intertwining signalling pathways.
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Affiliation(s)
- L R Ballou
- Department of Medicine, University of Tennessee, Memphis 38104, USA.
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14
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Abstract
Insulin is a polypeptide hormone consisting of 51 amino acids. Insulin promotes a variety of anabolic enzymatic pathways and inhibits many catabolic enzymatic pathways involved in energy storage, as well as in synthesis of structural tissue proteins. In addition, insulin serves as a growth factor, modulating mitogenesis, growth and differentiation. Insulin mediates all of its effects by initially binding and activating its specific cell-surface receptor. Conformational changes induced by insulin binding lead to activation of intrinsic receptor tyrosine kinase. Thus, the study of tyrosine kinase inhibitors, whether synthetically produced or purified from microorganisms or humans, has led to elucidation of molecular details of physiological insulin signaling.
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Affiliation(s)
- P R Srinivas
- Department of Internal Medicine, Wayne State University, Detroit, MI 48201
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15
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Sphingosine and Other Long-Chain Bases That Alter Cell Behavior. CURRENT TOPICS IN MEMBRANES 1994. [DOI: 10.1016/s0070-2161(08)60988-0] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
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16
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Sphingosine activates cellular diacylglycerol kinase in intact Jurkat cells, a human T-cell line. ACTA ACUST UNITED AC 1993. [DOI: 10.1016/0005-2760(93)90243-3] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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17
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Farese R, Standaert M, Yu B, Hernandez H, Cooper D. 2-Hydroxypropyl-beta-cyclodextrin enhances phorbol ester effects on glucose transport and/or protein kinase C-beta translocation to the plasma membrane in rat adipocytes and soleus muscles. J Biol Chem 1993. [DOI: 10.1016/s0021-9258(20)80679-6] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
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18
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Turinsky J, Nagel GW. Effect of sphingoid bases on basal and insulin-stimulated 2-deoxyglucose transport in skeletal muscle. Biochem Biophys Res Commun 1992; 188:358-64. [PMID: 1417855 DOI: 10.1016/0006-291x(92)92393-c] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Incubation of rat soleus muscles with 50 microM sphingosine or 50 microM sphinganine augmented basal 2-deoxy-D-glucose (2DG) transport 32%, but reduced the response to 0.1 and 1.0 mU insulin/ml by 17 and 27%, respectively. When the muscles were incubated with 50 microM phytosphingosine, a 63-93% increase in basal 2DG transport was observed. However, this treatment had no effect on insulin-stimulated 2DG transport. The phytosphingosine-induced increase in basal 2-DG transport was inhibited 93 and 98% with 35 and 70 microM cytochalasin B, respectively, suggesting that it is mediated by glucose transporters. Cellular accumulation of L-glucose, which is not mediated by glucose transporters, was not affected by phytosphingosine. It is concluded that (a) both sphingosine and sphinganine increase basal 2DG transport in muscle but diminish insulin-stimulated transport, and (b) phytosphingosine stimulates basal 2DG transport in muscle by a mechanism involving glucose transporters.
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Affiliation(s)
- J Turinsky
- Department of Physiology and Cell Biology, Albany Medical College, NY 12208
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19
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Gumà A, Muñoz P, Camps M, Testar X, Palacín M, Zorzano A. Inhibitors such as staurosporine, H-7 or polymyxin B cannot be used in skeletal muscle to prove the role of protein kinase C on insulin action. Biosci Rep 1992; 12:413-24. [PMID: 1290805 DOI: 10.1007/bf01121505] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
The precise role of protein kinase C in insulin action in skeletal muscle is not well defined. Based on the fact that inhibitors of protein kinase C block some insulin effects, it has been concluded that some of the biological actions of insulin are mediated via protein kinase C. In this study, we present evidence that inhibitors of protein kinase C such as staurosporine, H-7 or polymyxin B cannot be used to ascertain the role of protein kinase C in skeletal muscle. This is based on the following experimental evidences: a) staurosporine, H-7 and polymyxin B markedly block in muscle the effect of insulin on System A transport activity; however, this effect of insulin is not mimicked in muscle by TPA-induced stimulation of protein kinase C, b) H-7 and polymyxin B block insulin action on System A transport activity in an additive manner to the inhibitory effect of phorbol esters, c) staurosporine, H-7 and polymyxin B block the effect of insulin on lactate production, a process that is activated by insulin and TPA in an additive fashion, and d) staurosporine completely blocks the tyrosine kinase activity of insulin receptors partially purified from rat skeletal muscle.
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Affiliation(s)
- A Gumà
- Department de Bioquímica i Fisiologia, Facultat de Biologia, Universitat de Barcelona, Spain
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20
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Abstract
Ceramide has been suggested as an intracellular modulator of cell growth and differentiation [Okazaki, T. et al. (1990) J. Biol. Chem. 265, 15823-15831]. In this study, parameters that modulate the effects of ceramide on HL-60 cell growth and differentiation were examined. A short-chain, cell-permeable analog of ceramide, C2-ceramide, induced differentiation of HL-60 human leukemia cells and inhibited HL-60 growth in a concentration-dependent manner. The potency of C2-ceramide was modulated by the starting cell density such that the concentration of C2-ceramide producing 50% inhibition of cell growth (IC50%) ranged from 2 microM (for cells suspended at 1 x 10(5) cells/ml) to 11 microM (for cells at 8 x 10(5) cells/ml). However, the IC50% showed little variation if the concentration of C2-ceramide was expressed as fmol of C2-ceramide per 10(5) cells. Therefore, the effectiveness of C2-ceramide appeared to be primarily determined by its cellular rather than molar concentration. Binding of C2-ceramide to serum proteins resulted in a 10-fold increase in the IC50%. These results demonstrate that the biologic activity of C2-ceramide is subject to surface dilution kinetics and is sensitive to the presence of lipid-binding proteins. In these properties, ceramide behaves as a prototypic lipid second messenger/intracellular mediator.
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Affiliation(s)
- A Bielawska
- Department of Medicine, Duke University Medical Center, Durham, NC 27710
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21
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Cormont M, Gremeaux T, Tanti JF, Van Obberghen E, Le Marchand-Brustel Y. Polymyxin B inhibits insulin-induced glucose transporter and IGF II receptor translocation in isolated adipocytes. EUROPEAN JOURNAL OF BIOCHEMISTRY 1992; 207:185-93. [PMID: 1321040 DOI: 10.1111/j.1432-1033.1992.tb17036.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
In isolated adipocytes, polymyxin B inhibited insulin-induced glucose incorporation into lipids in a dose-dependent manner, while polymyxin E, a structurally related antibiotic, was ineffective. To approach the mechanism of this effect, the subcellular distribution of the glucose transporter Glut 4 was investigated. Adipocytes were pretreated without or with polymyxin B before insulin stimulation, subcellular fractionation was performed and Glut 4 was detected by immunodetection. Incubation of adipocytes with polymyxin B prevented the insulin-induced appearance of Glut 4 in the plasma membranes, but did not prevent their decrease from the low-density microsomal fraction. A lower purity of the plasma membrane fractions, a detergent effect of polymyxin B on the membranes or an interference of the substance with the immunodetection of the Glut 4 molecules were excluded. These results suggest that polymyxin B was interfering with the Glut 4 translocation process stimulated by insulin in adipocytes. In a similar fashion, polymyxin B inhibited the insulin-induced increase in IGF II binding to adipocytes. This resulted from a blockade of the appearance of IGF II receptors in the plasma membranes. Since low-molecular-mass GTP-binding proteins have been implicated in the regulation of vesicular trafficking, we have used [alpha-32P]GTP binding to analyze such proteins in adipocyte fractions, after SDS/PAGE and transfer to nitrocellulose. Specific and distinct subsets of GTP-binding proteins were revealed in plasma membrane and low-density microsomal fractions of control adipocytes, whether they were stimulated or not with insulin. Polymyxin B treatment of adipocytes markedly modified the profile of the low-molecular-mass GTP-binding proteins in plasma membranes, but not in low-density microsomal fractions. Our results suggest that polymyxin B was interfering with the exocytotic process of the Glut 4 and IGF II receptor-containing vesicles, perhaps at the fusion step between vesicles and plasma membranes.
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Affiliation(s)
- M Cormont
- Institut National de la Santé et de la Recherche Médicale, U 145, Faculté de Médecine, Nice, France
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22
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Farese RV, Standaert ML, Arnold T, Yu B, Ishizuka T, Hoffman J, Vila M, Cooper DR. The role of protein kinase C in insulin action. Cell Signal 1992; 4:133-43. [PMID: 1616820 DOI: 10.1016/0898-6568(92)90077-l] [Citation(s) in RCA: 46] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Affiliation(s)
- R V Farese
- Research Service, J. A. Haley Veterans' Hospital, Tampa, FL 33612
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23
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Abstract
Sphingosine inhibits autophosphorylation of the insulin receptor tyrosine kinase in vitro and in situ. This lysosphingolipid has been shown previously to inhibit the Ca2+/lipid-dependent protein kinase C. Here we show that insulin-dependent autophosphorylation of partially purified insulin receptor is half-maximally inhibited by 145 microM sphingosine (9 mol %) in Triton X-100 micelles. Half-maximal inhibition of protein kinase C autophosphorylation occurs with 60 microM sphingosine (3.4 mol %) in Triton X-100 mixed micelles containing phosphatidylserine and diacylglycerol. Sphingomyelin does not inhibit significantly the insulin receptor, suggesting that, as with protein kinase C, the free amino group may be essential for inhibition. Similar to the effects observed for protein kinase C, inhibition of the insulin receptor kinase by sphingosine is reduced in the presence of other lipids. However, the reduction displays a marked dependence on the lipid species: phosphatidylserine, but not a mixture of lipids compositionally similar to the cell membrane, markedly reduces the potency of sphingosine inhibition. The inhibition occurs at the level of the protein/membrane interaction: a soluble form of the insulin receptor comprising the cytoplasmic kinase domain is resistant to sphingosine inhibition. Lastly, sphingosine inhibits the insulin-stimulated rate of tyrosine phosphorylation of the insulin receptor in NIH 3T3 cells expressing the human insulin receptor. These results suggest that sphingosine alters membrane function independently of protein kinase C.
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Affiliation(s)
- R S Arnold
- Department of Chemistry, Indiana University, Bloomington 47405
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24
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Suzuki S, Sugawara K, Satoh Y, Toyota T. Insulin stimulates the generation of two putative insulin mediators, inositol-glycan and diacylglycerol in BC3H-1 myocytes. J Biol Chem 1991. [DOI: 10.1016/s0021-9258(18)92949-2] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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25
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Standaert ML, Sasse J, Cooper DR, Farese RV. Protein kinase C(19-31) pseudosubstrate inhibition of insulin action in rat adipocytes. FEBS Lett 1991; 282:139-42. [PMID: 2026249 DOI: 10.1016/0014-5793(91)80463-d] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Treatment of intact adipocytes with the autoregulatory PKC pseudosubstrate PKC(19-31) inhibited insulin-stimulated hexose uptake and lipogenesis, with no effect on basal values. The effect was dose-dependent with respective IC50 values of 30 microM and 600 microM for insulin-stimulated hexose uptake in electroporated and intact adipocytes. These studies indicate that PKC may play a role in the mediation of insulin action in adipocytes.
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Affiliation(s)
- M L Standaert
- James A. Haley Veterans' Administration Hospital, Tampa, FL 33612
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26
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Fujii Y, Kaizuka M, Hashida F, Maruo J, Sato E, Yasuda H, Kurokawa T, Ishibashi S. Insulin regulates Na+/glucose cotransporter activity in rat small intestine. BIOCHIMICA ET BIOPHYSICA ACTA 1991; 1063:90-4. [PMID: 2015265 DOI: 10.1016/0005-2736(91)90357-e] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
In order to examine the involvement of insulin in the activity of Na+/glucose cotransporter in rat small intestine, we compared Na(+)-dependent uptake of D-glucose by brush-border membrane vesicles prepared from control, streptozotocin-induced diabetic, insulin-treated diabetic and starved diabetic rats. In four groups, the uptake of D-glucose showed a transient overshoot in the presence of Na+ gradient between medium and vesicles (medium greater than vesicles). The overshoot magnitude was increased (1.8-fold of controls) in diabetic brush border membrane vesicles and recovered to the control level by the treatment of diabetic rats with insulin. In contrast, increased uptake of D-glucose in diabetic rats was not recovered by the starvation of diabetic rats although the blood glucose level was the same as that of controls. Furthermore, we attempted to examine phlorizin binding activities among four groups. Scatchard analysis indicated that phlorizin binding to diabetic brush border membrane vesicles was increased (1.6-fold of controls) without a change of the affinity for phlorizin as compared with controls. Increased binding of phlorizin to diabetic brush border membrane vesicles was also recovered to the control level by the treatment of diabetic rats with insulin, but not by starvation. These results suggested that the increased activity of Na+/glucose cotransporter in diabetic rats was due to the increase of the number of cotransporter and that intestinal cotransporter was physiologically controlled by insulin, but not by blood glucose levels.
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Affiliation(s)
- Y Fujii
- Department of Physiological Chemistry, Hiroshima University, School of Medicine, Japan
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27
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Epand RM, Stafford AR, Debanne MT. Action of insulin in rat adipocytes and membrane properties. Biochemistry 1991; 30:2092-8. [PMID: 1998671 DOI: 10.1021/bi00222a014] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Several small peptides inhibit insulin-promoted glucose uptake in rat adipocytes. At 10 microM peptide concentration, the extent of their inhibition of the insulin effect is related to the ability of these peptides to raise the bilayer- to hexagonal-phase transition temperature in model membranes. Hexane and DL-threo-dihydrosphingosine lower this phase transition temperature in model membranes, and they promote glucose uptake in adipocytes. There is thus an empirical relationship between the action of membrane additives on glucose uptake in adipocytes and their effect on the hexagonal-phase-forming tendency in model membranes. The most potent of the bilayer-stabilizing peptides tested in this work is carbobenzoxy-D-Phe-L-Phe-Gly. This peptide also inhibits insulin-stimulated protein synthesis in adipocytes. In contrast, DL-threo-dihydrosphingosine stimulates protein synthesis. The uptake of [125I]iodoinsulin by adipocytes is inhibited by carbobenzoxy-D-Phe-L-Phe-Gly. The mechanism of action of the bilayer-stabilizing peptides includes inhibition of insulin-dependent protein phosphorylation in adipocytes. The peptides are not specific inhibitors of a single function but are suggested to cause their effects by altering the physical properties of the membrane in a nonspecific manner. These results demonstrate that insulin-dependent functions of rat adipocytes can be modified by membrane additives in a manner predictable from the properties of these additives in model membranes.
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Affiliation(s)
- R M Epand
- Department of Biochemistry, McMaster University Health Sciences Centre, Hamilton, Ontario, Canada
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28
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Abstract
Sphingolipids have the potential to regulate cell behavior at essentially all levels of signal transduction. They serve as cell surface receptors for cytoskeletal proteins, immunoglobulins, and some bacteria; as modifiers of the properties of cell receptors for growth factors (and perhaps other agents); and as activators and inhibitors of protein kinases, ion transporters, and other proteins. Furthermore, the biological activity of these compounds resides not only in the more complex species (e.g., sphingomyelin, cerebrosides, gangliosides, and sulfatides), but also in their turnover products, such as the sphingosine backbone which inhibits protein kinase C and activates the EGF-receptor kinase, inter alia. Since sphingolipids change with cell growth, differentiation, and neoplastic transformation, they could be vital participants in the regulation of these processes.
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Affiliation(s)
- A H Merrill
- Department of Biochemistry, Emory University School of Medicine, Atlanta, Georgia 30322
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29
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Abstract
This comprehensive review was necessitated by recent observations suggesting that sphingomyelin and derivatives may serve second messenger functions. It has attempted to remain true to the theme of cellular signalling. Hence, it has focussed on the lipids involved primarily with respect to their metabolism and properties in mammalian systems. The enzymology involved has been emphasized. An attempt was made to define directions in which signals may be flowing. However, the evidence presented to date is insufficient to conclusively designate the mechanisms of stimulated lipid metabolism. Hence, the proposed pathways must be viewed as preliminary. Further, the biologic functions of these lipids is for the most part uncertain. Thus, it is difficult to presently integrate this sphingomyelin pathway into the greater realm of cell biology. Nevertheless, the present evidence appears to suggest that a sphingomyelin pathway is likely to possess important bioregulatory functions. Hopefully, interest in this novel pathway will grow and allow a more complete understanding of the roles of these sphingolipids in physiology and pathology.
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Affiliation(s)
- R N Kolesnick
- Program of Molecular Pharmacology and Therapeutics, Memorial Sloan-Kettering Cancer Center, Cornell University Medical Center, New York, NY 10021
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30
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Role of protein kinase C in the regulation of glucose transport in the rat adipose cell. Translocation of glucose transporters without stimulation of glucose transport activity. J Biol Chem 1991. [DOI: 10.1016/s0021-9258(18)52429-7] [Citation(s) in RCA: 29] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
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31
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Farese RV, Standaert ML, Ishizuka T, Yu B, Hernandez H, Waldron C, Watson J, Farese JP, Cooper DR, Wickstrom E. Antisense DNA downregulates protein kinase C isozymes (beta and alpha) and insulin-stimulated 2-deoxyglucose uptake in rat adipocytes. ANTISENSE RESEARCH AND DEVELOPMENT 1991; 1:35-42. [PMID: 1822247 DOI: 10.1089/ard.1991.1.35] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Rat adipocytes were treated with antisense dimethoxytrityl pentadecadeoxynucleotides, complementary to mRNA initiation codon regions for alpha and beta isozymes of protein kinase C (PKC). This antisense treatment provoked 50-70% decreases in PKC and insulin-stimulated 2-deoxyglucose uptake, but did not inhibit insulin-stimulated diacylglycerol synthesis. Sense or nonsense oligodeoxynucleotides were without effect on PKC and 2-deoxyglucose uptake. These results suggest that: (i) PKC-alpha and PKC-beta isozymes can be specifically downregulated in rat adipocytes by antisense oligodeoxynucleotides, and (ii) insulin-stimulated glucose transport requires PKC.
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Affiliation(s)
- R V Farese
- James A. Haley Veterans' Hospital, Department of Internal Medicine, Tampa, FL
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32
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33
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Insulin receptor tyrosine residues 1162 and 1163 control insulin stimulation of myristoyl-diacylglycerol generation and subsequent activation of glucose transport. J Biol Chem 1990. [DOI: 10.1016/s0021-9258(17)45354-3] [Citation(s) in RCA: 29] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
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34
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Standaert ML, Buckley DJ, Ishizuka T, Hoffman JM, Cooper DR, Pollet RJ, Farese RV. Protein kinase C inhibitors block insulin and PMA-stimulated hexose transport in isolated rat adipocytes and BC3H-1 myocytes. Metabolism 1990; 39:1170-9. [PMID: 2233279 DOI: 10.1016/0026-0495(90)90090-y] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Effects of protein kinase C (PKC) inhibitors and "down-regulation" on insulin and PMA-stimulated 2-deoxyglucose transport were determined in isolated rat adipocytes or BC3H-1 myocytes. In both model systems, H-7, sangivamycin, and staurosporine, inhibitors of the catalytic domain of PKC, each effectively blocked insulin and PMA-stimulated hexose uptake at similar concentrations. In the myocytes, staurosporine completely blocked the insulin effect retained post-chronic phorbol myristate acetate (PMA)-induced "down-regulation." These findings indicate (1) that chronic pretreatment with PMA may not lead to a complete loss of PKC activity in the myocyte, and (2) that PKC is involved in insulin-stimulated hexose transport in both isolated rat adipocytes and BC3H-1 myocytes.
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35
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Turinsky J, O'Sullivan DM, Bayly BP. 1,2-Diacylglycerol and ceramide levels in insulin-resistant tissues of the rat in vivo. J Biol Chem 1990. [DOI: 10.1016/s0021-9258(17)44844-7] [Citation(s) in RCA: 194] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
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36
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Ramachandran CK, Murray DK, Nelson DH. Dexamethasone increases neutral sphingomyelinase activity and sphingosine levels in 3T3-L1 fibroblasts. Biochem Biophys Res Commun 1990; 167:607-13. [PMID: 2157410 DOI: 10.1016/0006-291x(90)92068-b] [Citation(s) in RCA: 45] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
The activity of neutral sphingomyelinase (EC 3.1.4.12) in a plasma membrane enriched fraction was found to be increased in dexamethasone treated cells. The elevation of sphingomyelinase activity was blocked by cycloheximide indicating that protein synthesis was required for the steroid action. Ceramidase (EC3.5.1.23) activity was unaffected by the dexamethasone treatment. Levels of sphingosine in 3T3-L1 Cells were also increased after treatment with 10(-7) M dexamethasone for 2 and 4 hours.
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Affiliation(s)
- C K Ramachandran
- Department of Medicine, University of Utah School of Medicine, Salt Lake City 84132
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37
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Grunberger G, Levy J. Diacylglycerols modulate phosphorylation of the insulin receptor from human mononuclear cells. EUROPEAN JOURNAL OF BIOCHEMISTRY 1990; 187:191-8. [PMID: 2404758 DOI: 10.1111/j.1432-1033.1990.tb15294.x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
It has been found that 1,2- but not 1,3-diacylglycerols stimulated phosphorylation of the insulin receptor of cultured human monocyte-like (U-937) and lymphoblastoid (IM-9) cells both in the intact- and broken-cell systems. The stimulation of the receptor's beta-subunit phosphorylation was dose-dependent, with optimal effect at 100 micrograms/ml of diacylglycerol. The effects of insulin and 1,2-diacylglycerols on the phosphorylation of partially purified insulin receptors were additive. Phosphoamino acid analysis showed a major effect of diacylglycerols on phosphorylation of tyrosine residues. The diacylglycerols also stimulated tyrosine kinase activity of the partially purified U-937 and IM-9 insulin receptors 2.5-3.5-fold when measured by phosphorylation of an exogenous substrate, poly(Glu80Tyr20) in the absence of any added insulin, calcium or phospholipid. Since this diacylglycerol effect could not be reproduced under conditions optimal for protein kinase C activation and the purified protein kinase C did not stimulate phosphorylation of the beta-subunit of the insulin receptor in this system, it is unlikely that the diacylglycerol effect was mediated by protein kinase C. Since these exogenous 1,2-diacylglycerols at the same high concentration also inhibited 125I-insulin binding to the insulin receptor of the intact U-937 and IM-9 cells, diacylglycerols could modulate the function of the insulin receptor and insulin action in human mononuclear cells.
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Affiliation(s)
- G Grunberger
- Department of Internal Medicine, Wayne State University School of Medicine, Detroit
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38
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Zhang H, Buckley NE, Gibson K, Spiegel S. Sphingosine stimulates cellular proliferation via a protein kinase C-independent pathway. J Biol Chem 1990. [DOI: 10.1016/s0021-9258(19)40197-x] [Citation(s) in RCA: 184] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
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39
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Murray DK, Hill ME, Nelson DH. Inhibitory action of sphingosine, sphinganine and dexamethasone on glucose uptake: studies with hydrogen peroxide and phorbol ester. Life Sci 1990; 46:1843-9. [PMID: 2362544 DOI: 10.1016/0024-3205(90)90236-k] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
The mechanism of the inhibitory action of glucocorticoids on glucose uptake is incompletely understood. Treatment with corticosteroids of cells in which glucose uptake is stimulated at insulin postbinding and postreceptor sites may clarify the site of the steroid inhibitory action. Hydrogen peroxide, which has been shown to stimulate the insulin receptor tyrosine kinase, and phorbol myristate acetate (PMA) which stimulates protein kinase C were, therefore, used as stimulators of glucose transport in this study. These studies demonstrate that dexamethasone and the sphingoid bases, sphinganine and sphingosine, inhibit glucose uptake that has been stimulated at either the receptor kinase or protein kinase C level in both 3T3-L1 and 3T3-C2 cells. These data confirm glucocorticoid inhibitory action at a post binding level and support the suggestion that some corticosteroid inhibitory effects may be mediated by an action on sphingolipid metabolism.
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Affiliation(s)
- D K Murray
- Department of Medicine, University of Utah School of Medicine, Salt Lake City 84132
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40
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Saltiel AR, Osterman DG, Darnell JC, Sorbara-Cazan LR, Chan BL, Low MG, Cuatrecasas P. The function of glycosyl phosphoinositides in hormone action. Philos Trans R Soc Lond B Biol Sci 1988; 320:345-58. [PMID: 2906143 DOI: 10.1098/rstb.1988.0081] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
The molecular events involved in the cellular actions of insulin remain unexplained. Some of the acute actions of the hormone may be due to the intracellular generation of a chemical substance which modulates certain enzyme activities. Such an enzyme-modulating substance has been identified as an inositol phosphate-glycan, produced by the insulin-sensitive hydrolysis of a glycosyl-phosphatidylinositol (glycosyl-PtdIns) precursor. This precursor glycolipid is structurally similar to the glycosyl-phosphoinositide membrane protein anchor. The exposure of fat, liver or muscle cells to insulin results in the hydrolysis of glycosyl-PtdIns, giving rise to the inositol phosphate glycan and diacylglycerol. This hydrolysis reaction is catalysed by a glycosyl-PtdIns-specific phospholipase C. This enzyme has been characterized and purified from a plasma membrane fraction of liver. This reaction also results in the acute release of certain glycosyl-PtdIns-anchored proteins from the cell surface. Elucidation of the functional role of glycosyl-phosphoinositides in the generation of second messengers or the release of proteins may provide further insights into the pleiotropic nature of insulin action.
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Affiliation(s)
- A R Saltiel
- Laboratory of Biochemical Endocrinology, Rockefeller University, New York 10021
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