Adipose Tissue-Specialized Immunologic Features Might Be the Potential Therapeutic Target of Prospective Medicines for Obesity

Excessive lipid accumulation in adipose tissue is either the source of obesity or the cause and result of chronic local inflammation, and recent studies indicate that the accumulation may induce many other specialized immunologic features with macrophages and epidemic diseases. We analyze the effective stages of immune cells in adipose tissue, including macrophage recruitment, macrophage polarization, and macrophage-like phenotype preadipocyte possession to find optimal sites as drug targets. Subsequently, some main signaling pathways are summarized in this review, including the AMP-activated protein kinase (AMPK) pathway, the JNK signaling pathway, and a novel one, the Notch signaling pathway. We illustrate all these points in order to determine the general pathogenesis of chronic low-grade local inflammation in adipose tissue and the related signaling pathways. In addition, signal-associated prospective compounds, such as berberine, are summarized and discussed with potential targets in pathogenesis. This might provide some possible thoughts and novel therapies for studying chronic inflammatory diseases, such as insulin resistance and type 2 diabetes mellitus.

AMP kinase promotes Bcl6 expression in both mouse and human T cells

The transcription factor Bcl6 is a master regulator of follicular helper T (T_FH) cells, and understanding the signaling pathway that induces Bcl6 and T_FH cell differentiation is therefore critical. IL-2 produced during T cell activation inhibits Bcl6 expression but how T_FH cells evade IL-2 inhibition is not completely understood. Here we show that Bcl6 is highly up-regulated in activated CD4 T cells following glucose deprivation (GD), and this pathway is insensitive to inhibition by IL-2. Similar to GD, the glucose analog 2-deoxyglucose (2DG) inhibits glycolysis, and 2DG induced Bcl6 expression in activated CD4 T cells. The metabolic sensor AMP kinase (AMPK) is activated when glycolysis is decreased, and the induction of Bcl6 by GD was inhibited by the AMPK antagonist compound C. Additionally, activation of AMPK by the drug AICAR caused Bcl6 up-regulation in activated CD4 T cells. When mice were immunized with KLH using AICAR as an adjuvant, there was a strong T_FH-dependent enhancement of KLH-specific antibody (Ab) responses, and higher Bcl6 expression in T_FH cells in vivo. Activation of AMPK strongly induced BCL6 and the up-regulation of T_FH cell marker expression by human CD4 T cells. Our data reveal a major new pathway for T_FH cell differentiation, conserved by both mouse and human T cells. Mature T_FH cells are reported to have a lower metabolic state compared to T_H1 cells. Our data indicates that decreased metabolism may be deterministic for T_FH cell differentiation, and not simply a result of T_FH cell differentiation.

Adenylate kinase 5 autoimmunity in treatment refractory limbic encephalitis

We report two men with limbic encephalitis (LE) refractory to corticosteroids, IVIg and plasma exchange. Both patients had serum/CSF antibodies that reacted with the cytoplasm of neurons. Probing of a hippocampal cDNA library resulted in the isolation of adenylate kinase 5 (AK5). Patients' antibodies, but not those of 111 controls, recognized AK5-expressing phage plaques. Human AK5-affinity purified antibodies reproduced the neuronal immunolabeling of patients' antibodies, and co-localized with a rabbit AK5 antibody, confirming that the brain autoantigen was AK5. Detection of antibodies to AK5 in LE patients carries a poor prognosis, and suggests the prompt use of aggressive immunosuppression.

[Expression of adenylate kinase of Schistosoma japonicum and evaluation on the immunoreactivity of the recombinant protein]

OBJECTIVE

To express and purify the Schistosoma japonicum adenylate kinase (AK) protein of which the cDNA sequence was subcloned into the pET32a(+) soluble expression plasmid, and to evaluate its immunoreactivity.

METHODS

The recombinant plasmid was transformed into E. coli BL21, and induced with IPTG for expression. The bacterial lysis was conducted by ultrasonication and the supernatant was analyzed by SDS-PAGE after boiling and centrifugation. The target protein was purified with the Ni-NTA agarose. The proteins on the gel were transferred to the PVDF film and then the immunoreactivity was tested by Western blotting using anti-6-His antibody, sera from rabbits 6 weeks after infected with cercariae or UV-attenuated cercariae. The purified protein was coated for ELISA to test the cercariae infected rabbit serum and the normal rabbit serum.

RESULTS

The molecular weight of the target fusion protein was Mr 40 000 after being induced with IPTG. The fused protein showed a single band when reacted with anti-6-His antibody, the cercariae infected rabbit serum and attenuated cercariae infected rabbit serum.

CONCLUSION

The AK protein is expressed as a fused protein with thioredoxin and its molecular weight is about Mr 40000. This protein has a positive immunoreactivity with sera of rabbits infected with cercariae and UV-attenuated cercariae.

Antibody-antigen interactions measured by surface plasmon resonance: global fitting of numerical integration algorithms

The interactions between adenylate kinase (AK) and a monoclonal antibody against AK (McAb3D3) were examined by means of optical biosensor technology, and the sensograms were fitted to four models using numerical integration algorithms. The interaction of a solution of McAb3D3 with immobilized AK follows a double exponential function and the data fitted well to an inhomogeneous ligand model. The interaction of a solution AK with immobilized McAb3D3 follows a single exponential function and the data fitted well to a pseudo-first order reaction model. The true association constants of AK binding to McAb3D3 in solution were obtained from competition BIAcore measurements. The difference in results obtained with solid-phase BIAcore and competition BIAcore may be due to rebinding of the dissociated analyte to the immobilized surface. The results obtained with BIAcore are compared to those obtained by ELISA methods. We suggest that the best method for analysis of BIAcore data is direct, global fitting of sensorgrams to numerical integration algorithms corresponding to the different possible models for binding.

Cellular distribution and developmental expression of AMP-activated protein kinase isoforms in mouse central nervous system

The mammalian AMP-activated protein kinase is a heterotrimeric serine/threonine protein kinase with multiple isoforms for each subunit (alpha, beta, and gamma) and is activated under conditions of metabolic stress. It is widely expressed in many tissues, including the brain, although its expression pattern throughout the CNS is unknown. We show that brain mRNA levels for the alpha2 and beta2 subunits were increased between embryonic days 10 and 14, whereas expression of alpha1, beta1, and gamma1 subunits was consistent at all ages examined. Immunostaining revealed a mainly neuronal distribution of all isoforms. The alpha2 catalytic subunit was highly expressed in neurons and activated astrocytes, whereas the alpha1 catalytic subunit showed low expression in neuropil. The gamma1 noncatalytic subunit was highly expressed by neurons, but not by astrocytes. Expression of the beta1 and beta2 noncatalytic subunits varied, but some neurons, such as granule cells of olfactory bulb, did not express detectable levels of either beta isoform. Preferential nuclear localization of the alpha2, beta1, and gamma1 subunits suggests new functions of the AMP-activated protein kinase, and the different expression patterns and cellular localization between the two catalytic subunits alpha1 and alpha2 point to different physiological roles.

Evidence for in vivo synthesis of thiamin triphosphate by cytosolic adenylate kinase in chicken skeletal muscle

We showed previously that cytosolic adenylate kinase (AK1) purified from pig skeletal muscle catalyzes in vitro formation of thiamin triphosphate (TTP) from thiamin diphosphate (TDP) and ADP in addition to ATP formation from ADP [Shikata, H. et al. (1989) Biochem. Int. 18, 933-942]. To obtain evidence for in vivo synthesis of TTP by AK1, changes in TTP content and AK1 activity were determined in chicken skeletal muscle during development after hatching. Thiamin phosphate metabolism in chicken skeletal muscle was also studied. i) An extremely high TTP content, 81% of total thiamin (thiamin plus thiamin phosphates), was detected in the white (fast-twitch) muscle of adult normal chicken (5th to 9th month) compared with a relatively high TTP content of 31% in the red (slow-tonic) muscle. Since approximately equivalent amounts of total thiamin were present in the two types of muscle, the ratio of TTP to TDP was high (5.0) in the white muscle and low (0.41) in the red muscle. ii) Rabbit anti-chicken AK1 antiserum against the purified chicken cytosolic AK1 preparation was obtained. Both AK1 activity and TTP-synthesizing activity in crude cytosol fraction of adult chicken white muscle were inhibited in parallel by the antiserum. iii) In the white muscle of normal chicken, the TTP content and AK1 activity responsible for forming either ATP or TTP were increased in a parallel manner up to day 16 after hatching, after which both remained constant. In the red muscle, on the other hand, both the TTP content and the AK1 activity were low in comparison with those in the white muscle, and were almost constant after hatching.(ABSTRACT TRUNCATED AT 250 WORDS)

Multiforms of mammalian adenylate kinase and its monoclonal antibody against AK1

An attempt has been made to determine the intracellular distribution of the multiforms of the adenylate kinase (AK) isoenzymes in mammalian tissues, to shed some light on their physiological roles, especially in energy metabolism. The adenylate kinase zymograms obtained from isoelectric focusing yielded two typical isoform patterns: (1) with a pI greater than or equal to 9 and 8.6, specific for bovine skeletal muscle, heart, aorta and brain, and (2) with a pI = 7.9 and 7.1, specific for liver and kidney. Pattern (1) was attributed to the cytosolic isoenzyme (AK1) as demonstrated by immunostaining with anti-AK1. Pattern (2) was attributed to the mitochondrial isoenzyme (AK2). These results were largely confirmed by chromatofocusing experiments. The AK1 isoenzyme was partially purified from the cytosol fraction of bovine aortic smooth muscle and had an apparent Mr of 23.5 kilodaltons. Its kinetic features are discussed from a comparative standpoint. Finally, the human serum AK1 isoform was also detected by Western blotting with a monoclonal antibody directed against crystalline porcine muscle AK1. These results are to form the basis of further studies on the 'aberrant' adenylate kinase isoenzyme from the serum of Duchenne muscular dystrophics.

Site specific antibodies directed to the ATP binding region of some kinases

Polyclonal antibodies raised in rabbits to ATP-requiring enzymes such as 3-phosphoglycerate kinase show cross-reactivity against other unrelated kinases. Our results show that rabbit polyclonal antiserum possesses antibodies that recognize an antigenic site at the ATP binding region of kinases. A classical immunotitration curve was obtained when hexokinase was titrated against anti-myokinase IgG. The immunoinhibitions was reversed in the presence of small concentration of ATP. This cross-reactivity between site specific antibody and unrelated kinase demonstrates the existence of an antigenic site around the ATP binding region. Our proposal of the existence of a common antigenic determinant in the ATP binding region is in agreement with the finding of a common structural domain that binds ATP.

Antigenic structure of adenylate kinase from porcine skeletal muscle. IV. Two antigenic determinants on carboxyl-terminal peptide 126-194

Delineation of the location(s) of antigenic activity in CNBr peptide 126-194 from porcine skeletal muscle adenylate kinase (AK) was attempted. Peptide 126-194 was digested with chymotrypsin, Staphylococcus aureus V8 protease and trypsin, and several short peptides were purified from the digests by reverse-phase high-performance liquid chromatography (HPLC). Inhibition of the binding of radioiodinated peptide 126-194 to goat antibody to porcine skeletal muscle AK (anti-AK antibody) by the peptides obtained by the enzymatic cleavages was examined by solid phase radioimmunoassay (RIA). At least two antigenic determinants have been identified from the results. One is in the amino (N)-terminal half region 126-154, especially in the vicinity of 131-144, and the other is in the carboxyl (C)-terminal half region 165-183, especially in the vicinity of 165-171. Both of them seem to correspond to exposed and accessible regions in the three-dimensional structure of AK. The correlation between antigenicity and high mobility of the loop in the estimated antigenic region 131-144 is also discussed.

Mitochondrial adenylate kinase (AK2) from bovine heart. The complete primary structure

The sequence analysis of adenylate kinase isoenzyme 2 (AK2) was completed using a gas-phase sequencer constructed in our laboratory. The enzyme contains 238 amino acid residues in the following order: (sequence; see text) The four cysteine residues of AK2 were reinvestigated. Cys-41 and Cys-233 contain free thiols, which can be carboxymethylated in the intact protein without loss of enzymic activity. Chemical and model-building studies suggest that the pair Cys-43/Cys-93 forms a disulfide in native AK2. The relative molecular mass of AK2, as deduced from the sequence, is 26104. Other methods, including titration of -SH groups, sedimentation equilibrium ultracentrifugation and gel filtration yielded Mr values in the range from 26 000 to 31 500, each value depending on the respective method of determination. Bovine heart AK2 contains 44 residues more than the homologous isoenzyme AK1 (myokinase). As all but one single insertions and deletions cancel, the higher Mr of AK2 is due to 9 residues preceding the N terminus of AK1, a stretch of 30 residues in the middle of the molecule and 6 residues at the end. AK2 and AK1 are similar in their active-site geometry. In contrast, AK2 does not possess any of the three antigenic sites of AK1, which is consistent with the lack of immunological cross-reactivity between AK1 and AK2.

Antigenic structure of adenylate kinase from porcine skeletal muscle--II. Immunochemical cross-reactivity of fragments from adenylate kinase

Specific antibody to a fragment [CBb(2-56)] of porcine muscle adenylate kinase was purified from goat antiserum against adenylate kinase on an immunoadsorbent column. This anti-CBb antibody cross-reacted in solid phase radioimmunoassay with two other CNBr-fragments of adenylate kinase, CBfN(81-125) and CBfC(126-194). This cross-reactivity explained their high inhibition activities in quantitative precipitin reaction between adenylate kinase and goat antiserum shown in the previous work. Cysteinyl residues of the enzyme (positions 25 and 187) were S-cyanylated with 2-nitro-5-thiocyanobenzoic acid and the enzyme was cleaved at these residues. Fragment 1-24 thus obtained was purified. The fragment 1-24, composing the N-terminal half of CBb(2-56), accounted for full activity of CBb to anti-CBb in radioimmunoassay. Hence antigenic region(s) of CBb(2-56) exist in its N-terminal half, 2-24, and this determinant(s) may be closely related to the cross-reactivity among CB-fragments. CBfN also bound to the antibody fraction which had not been adsorbed to CBb-Sepharose (non-anti-CBb). CBfN carried additional antigenic regions. In conclusion, we propose that the antigenic reactive region(s) of adenylate kinase responsible for the cross-reactivity of the CB-fragments are as follows: -Glu-Glu-Lys-Leu-Lys-Lys- (2-7), -Glu-Glu-Phe-Lys-Arg-Lys- (103-108), -Glu-Glu-Thr-Ile-Lys-Lys- (143-148).

Antigenic structure of adenylate kinase from porcine skeletal muscle. I. Three immunochemically active peptides obtained by cleavage with cyanogen bromide

Analysis of the quantitative precipitin reaction of adenylate kinase from porcine skeletal muscle with goat anti-adenylate kinase antiserum indicated that there are at least four antigenic determinants on the enzyme molecule. Porcine adenylate kinase was cleaved with cyanogen bromide, and four peptides were fractionated by ion-exchange chromatographies. Three fragments, CBb (2-56), CBfN (81-125), and CBfC (126-194), inhibited the quantitative precipitin reaction of intact adenylate kinase with goat antiserum. CBb, CBfN, and CBfC also inhibited the binding of 125I-labeled adenylate kinase to the specific antibody purified from goat antiserum. In both inhibition studies, the inhibitory activity of each fragment was extremely high, and reached 70% or more in the latter case. From these results and in view of the presence of the sequence -Glu-Glu-X-X'-Lys (or Arg)-Lys- in each immunochemically active fragment, we suggest that these fragments have similar antigenic determinants which are cross-reactive.

Purification and characterization of adenylate kinase isozymes from rat muscle and liver

Isozymes of adenylate kinase (ATP:AMP phosphotransferase, EC 2.7.4.3) were purified from skeletal muscle and liver of rats to essentially homogeneous states by acrylamide gel electrophoresis and sodium dodecyl sulfate gel electrophoresis. The isozyme from muscle was purified by acidification to pH 5.0, and column chromatography on phosphocellulose, Sephadex G-75 and Blue Sepharose CL-6B, while that from liver was purified by column chromatography on Blue Sepharose CL-6B, Sephadex G-75 and carboxymethyl cellulose. By these procedures the muscle isozyme was purified about 530-fold in 29% yield, and the liver isozyme about 3600-fold in 27% yield from the respective tissue extracts. The molecular weights of the muscle and liver isozymes were estimated as about 23 500 and 30 500, respectively, by both sodium dodecyl sulfate gel electrophoresis and molecular sieve chromatography, and no subunit of either isozyme was detected. The isoelectric points of the muscle and liver isozymes were 7.0 and 8.1, respectively. The Km values of the respective enzymes for ATP and ADP were similar, but the Km(AMP) of the liver isozyme was about one-fifth of that of the muscle isozyme. Immunological studies with rabbit antiserum against the rat muscle isozyme showed that the muscle isozyme was abundant in muscle, heart and brain, while the liver isozyme was abundant in liver and kidney.

Sero-genetic studies on the Dama of South West Africa

The Dama of South West Africa are a Negroid people living as a reproductive isolate in the desert and semi-desert areas of the north-west of the country. Until recent times a large proportion of them were held in bondage by the Khoikhoi (Hottentot) Nama, while the rest lived as hunter-gatherers in the mountains. This study and the work of Knussmann and Knussmann indicate that they are a Negro people, which probably has been cut off over a period from contact with other Negroes. They have received very little genetic contribution from the Khoikhoi or the San (Bushmen). The results of this investigation of 24 blood genetic marker systems in a carefully selected random sample of Dama support these conclusions.