Biomedical subjects

X J Sun

Publications and source records attributed to X J Sun.

At least 19 recordsLinked to original sources

PubMed2005

Enhancement of radiation sensitivity with BH3I-1 in non-small cell lung cancer.

BACKGROUND: Anti-apoptotic proteins, such as Bcl-2 and Bcl-xL, are frequently over-expressed in human malignancies, and this is correlated with resistance to chemotherapeutic drugs and gamma- radiation. Recently identified small organic molecules capable of inhibiting Bcl-2 and/or Bcl-xL function, may enhance radiation sensitivity of cancer cells in which they are over expressed. We examined whether specific blockade of the BH3-domain binding to Bcl-xL could sensitize cancer cells to gamma- radiation. METHODS: Human non-small-cell lung cancer H460 cells with wild-type p53 and H1792 cells with mutant p53 were exposed to various doses of radiation and/or BH3I-1 and for different points of time to BH3I-1 treatment. XTT and clonogenic survival assays were used to evaluate the growth-inhibitory effects of the antagonist BH3I-1, ionizing radiation or both. Western blot analysis was used to examine the cellular effect of the expression of Bcl-xL, Bax, and p53. Apoptosis and cell cycle distribution were analyzed by confocal microscopy with Hoechst 33258 staining and cytochrome c, and flow cytometry, respectively. RESULTS: BH3I-1 appeared to induce a dose- and time-dependent apoptosis in H460 and H1792 cells, regardless of p53 status. After 2 days of BH3I-1 treatment, the cells that remained attached were exposed to ionizing radiation. Followed by clonogenic assay, BH3I-1 treatment enhanced the radiation sensitivity of H1792 surviving cells with mutant p53, but not in H460 cells with wild-type p53. A transient time-dependent cell cycle blockade at G2-M phase was identified for H1792 cells without subsequent modification of cell cycle distribution. CONCLUSION: These findings suggest a potential role for the small molecule inhibitor as a novel radiation sensitizer in non-small cell lung cancer.

Carcinoma, Non-Small-Cell Lung↗

PubMed2001

Enhanced expression of insulin receptor substrate-2 and activation of protein kinase B/Akt in regenerating pancreatic duct epithelium of 60 %-partial pancreatectomy rats.

AIMS/HYPOTHESIS: Early compensatory mechanisms of regeneration following partial pancreatectomy involve ductal proliferation and, subsequently, differentiation into acinar and endocrine cell types, although it is not clear how these processes are regulated. We investigated the expression and roles of insulin receptor substrate-2 (IRS-2) and protein kinase B/Akt (Akt) in pancreatic regeneration that starts with the common duct epithelium using a non-diabetic model of beta cell adaptation and mass expansion, 60 %-pancreatectomy rats. METHODS: We used confocal immunofluorescence microscopy to study IRS-2 and Akt expression and activation in pancreatic common ducts at intervals after surgery. These proteins were studied in relation to proliferation markers and insulin immunostaining. RESULTS: In pancreatectomized rats, a short-term increase in proliferation was observed in the common duct epithelial lining ( approximately 4-fold) compared with sham-operated control rats which correlated with about a 1.8-fold increase in IRS-2 immunoreactivity 2 days after surgery. Interspersed with proliferating cells of the common duct, evaginations were rare single and clustered insulin immunopositive cells which expressed high levels of IRS-2 immunoreactivity. Epithelium of duct evaginations from 2-day post-Px rats exhibited striking phospho-Akt staining ( approximately 3.5-fold above control rats) without any detectable changes in total Akt staining. CONCLUSION/INTERPRETATION: Our data suggest that IRS-2 plays an important role in pancreatic regeneration and growth by mediating duct proliferation and by maintaining the differentiated beta cell. The restricted staining pattern of phospho-Akt to cells of the common duct evaginations suggests that it has a role in regulating post-mitotic events related to cell-specific gene expression or survival or both.

Animals↗

PubMed2001

Targeted disruption of the mouse estrogen sulfotransferase gene reveals a role of estrogen metabolism in intracrine and paracrine estrogen regulation.

Elicitation of biological responses by estrogen in target tissues requires the presence of ER as well as receptor-active ligand in the local microenvironment. Though much attention has been devoted to the study of the receptor in estrogen target tissues, the concept is emerging that tissue estrogen sensitivity may also be regulated by ligand availability through metabolic transformation in situ. Here, we show that targeted disruption, in the mouse, of an estrogen metabolic enzyme, estrogen sulfotransferase (EST), causes structural and functional lesions in the male reproductive system. EST catalyzes the sulfoconjugation and inactivation of estrogen and is expressed abundantly in testicular Leydig cells. Although knockout males were fertile and phenotypically normal initially, they developed age-dependent Leydig cell hypertrophy/hyperplasia and seminiferous tubule damage. Development of these lesions in the testis could be recapitulated by exogenous E2 administration in younger knockout mice, suggesting that they arose in older knockout mice from chronic estrogen stimulation. Older knockout mice were also found to have reduced testis and epididymis weights but increased seminal vesicle/coagulating gland weight because of tissue swelling. Furthermore, total and forward sperm motility of older knockout mice was reduced by 60% and 80%, respectively, and these mice produced smaller litters compared with age-matched wild-type males. These findings establish a role for EST in the male reproductive system and indicate that intracrine and paracrine estrogen activity can be modulated by a ligand transformation enzyme under a physiological setting. Thus, inhibition of estrogen metabolic enzymes by environmental chemicals, as has been demonstrated recently for the human EST, may constitute a novel mechanism of endocrine disruption in vivo.

Aging↗

PubMed2001

[Research on automatic diagnosis system of electrocardiogram].

The duration of QRS wave, P wave and T wave of ECG can be computerized and auto-detected with digital signal process and wave recognition technology. It can diagnose 15 kinds of abnormal ECG such as ventricular presystole automatically and print out corresponding diagnosis reports. In order to verify the system's stability and creditability, we used American MIT-BIH database to test our algorithms and got a good result.

Algorithms↗

PubMed2000

Neurite morphogenesis of identified visual interneurons and its relationship to photoreceptor synaptogenesis in the flies, Musca domestica and Drosophila melanogaster.

The first neuropile, or lamina, of the fly's optic lobe comprises a model set of identified neurons that are arrayed in cylindrical modules, called cartridges. The cartridge acquires adult form only in the second half of the fly's pupal life. All cells are by then correctly located within each of the lamina's cartridges (Drosophila, Musca), becoming invested by glial cells after 75% of pupal development (P + 75%). In adult cartridges, two lamina cells, L1 and L2, receive input from photoreceptor terminals R1-R6, at so-called tetrad synapses that form in the pupa when these cells' dendrites contact R1-R6. Single-section electron microscopy (EM, Drosophila) and serial-EM reconstructions of L1 and L2 (Musca) reveal relationships between the morphogenesis of L1/L2 dendrites and the formation of tetrads. Neurite outgrowth is initially (P + 55%) random and neurites are unbranched; many neurites invaginate surrounding terminals of R1-R6 but, later, embrace the outer surfaces of these. The maximum profusion of neurites at P + 74% coincides with peak numbers of nascent tetrads; neurites then branch vertically, in the lamina's depth. Later, neurites failing to reach R1-R6's outer surfaces regress. Down the length of their axons, L1 and L2's neurites initially form a random sequence, L1 partnering L1 as often as L2, etc., but beginning at P + 74%, L1 partners L2, and L2 partners L1, with progressive strictness. L1 has more neurites overall than L2. These observations are consistent with the following hypotheses: a neurite only survives if it contacts a presynaptic site; a synapse only survives if it progressively acquires the appropriate number and combination of postsynaptic neurites, culminating in a tetrad; an interaction exists between the neurites of L1 and L2, so that the growth of one respects the pattern of growth of the other.

Animals↗

PubMed2000

[Derivative gas chromatographic analysis of fructooligosaccharide in fermented sucrose].

As a new sweetener, fructooligosaccharide is paid more and more attention for its health improvement property. It includes trisaccharide, tetrasaccharide and pentasaccharide, and can be produced from sucrose by the fermentation of microorganism. In order to analyze the content of fructooligosaccharide in fermented sugar by gas chromatography, fructooligosaccharide was transformed into trimethylsilyl derivatives. Based on the modified gas chromatograph SP2308, and under the chosen chromatographic conditions with 0.53 mm capillary column of OV-101, the contents of fructose, glucose, sucrose and fructooligosaccharide were determined by programmed temperature chromatography. The recovery of fructooligosaccharide was satisfactory.

Chromatography, Gas↗

PubMed1999

Identification of enhanced serine kinase activity in insulin resistance.

Insulin receptor substrate (IRS) proteins play a crucial role as signaling molecules in insulin action. Serine phosphorylation of IRS proteins has been hypothesized as a cause of attenuating insulin signaling. The current study investigated serine kinase activity toward IRS-1 in several models of insulin resistance. An in vitro kinase assay was developed that used partially purified cell lysates as a kinase and glutathione S-transferase fusion proteins that contained various of IRS-1 fragments as substrates. Elevated serine kinase activity was detected in Chinese hamster ovary/insulin receptor (IR)/IRS-1 cells and 3T3-L1 adipocytes chronically treated with insulin, and in liver and muscle of obese JCR:LA-cp rats. It phosphorylated the 526-859 amino acid region of IRS-1, whereas phosphorylation of the 2-516 and 900-1235 amino acid regions was not altered. Phosphopeptide mapping of the 526-859 region of IRS-1 showed three major phosphopeptides (P1, P2, and P3) with different patterns of phosphorylation depending on the source of serine kinase activity. P1 and P2 were strongly phosphorylated when the kinase activity was prepared from insulin-resistant Chinese hamster ovary/IR/IRS-1 cells, weakly phosphorylated by the kinase activity from insulin-resistant 3T3-L1 adipocytes, and barely phosphorylated when the extract was derived from insulin-resistant liver. In contrast, P3 was phosphorylated by the serine kinase activity prepared from all insulin-resistant cells and tissues of animals. P1 and P2 phosphorylation can be explained by mitogen-activated protein kinase activity based on the phosphopeptide map generated by recombinant ERK2. In contrast, mitogen-activated protein kinase failed to phosphorylate the P3 peptide, suggesting that another serine kinase regulates this modification of IRS-1 in insulin-resistant state.

Animals↗

PubMed1999

Insulin-induced insulin receptor substrate-1 degradation is mediated by the proteasome degradation pathway.

Insulin receptor substrate (IRS) proteins are important intracellular molecules that mediate insulin receptor tyrosine kinase signaling. A decreased content of IRS proteins has been found in insulin-resistant states in animals, humans, and cultured cells under various conditions. However, the molecular mechanism that controls cellular levels of IRS proteins is unknown. We report that chronic insulin treatment induces the degradation of IRS-1, but not IRS-2, protein in cultured cells. The insulin-induced degradation of IRS-1 can be prevented by pretreatment with lactacystin, a specific inhibitor for proteasome degradation. These data demonstrate, for the first time, that insulin-induced degradation of IRS-1 is mediated by the proteasome degradation pathway. IRS-2 can escape from the insulin-induced proteasome degradation, suggesting the existence of specific structural requirements for this degradation process.

Adenosine Triphosphatases↗

PubMed1998

Developmental anatomy of the Drosophila brain: neuroanatomy is gene expression.

On-line databases of anatomical information are being compiled for a number of genetically manipulable organisms, including the fruit fly, Drosophila melanogaster. Based on the success of the molecular databases that preceded them, they face formidable problems in data cataloguing, storage, and retrieval. The prospect for such databases, which is apparent already, is to alter permanently the approach to neuroanatomy in such species. Experience with Drosophila indicates the possibility to arbitrate controversies over and, in some cases, to redefine the borders drawn in the brain by conventional neuroanatomical methods. Two publications in this issue of Journal of Comparative Neurology by Nassif et al. and by Hartenstein et al. highlight one of the first demonstrations of a further opportunity in Drosophila. In some cases, it is already possible to suggest how individual cellular elements--neurons, tracts, and neuropil regions--might be traced from the time when they first express a precocious marker, such as the product of the fasciclin-II gene, through the metamorphic pupal stage, and into the adult. In this way, it becomes possible to identify the structures of the adult brain from the time of their first emergence in the embryo and to follow their transitional positions throughout the course of development. Critical in this process is the neuroanatomical organization of the larval brain, which contains not only the fully functional central nervous system of the larva but also the developing elements of the adult brain, because this holds the key to understanding both the cellular elements that are inherited from the embryo and the elements that are in the process of forming the adult nervous system.

Animals↗

PubMed1998

Mechanism of the dynorphin-induced dualistic effect on free intracellular Ca2+ concentration in cultured rat spinal neurons.

In order to study the different mechanisms of dynorphin spinal analgesia and neurotoxicity at low and high doses, the effects of various concentrations of dynorphin A-(1-17) on the free intracellular Ca2+ concentration ([Ca2+]i) in the cultured rat spinal neurons were studied using single cell microspectrofluorimetry. While dynorphin A-(1-17) 0.1-100 microM had no significant effect on basal [Ca2+]i, dynorphin A-(1-17) 0.1 and 1 microM significantly decreased the high KCl-evoked peak [Ca2+]i by 94% and 83% respectively. Dynorphin A-(1-17) 10 and 100 microM did not affect the peak [Ca2+]i following K+ depolarization, but in all these neurons there was a sustained and irreversible rise in [Ca2+]i following high-K+ challenge. Pretreatment with the specific kappa-opioid receptor antagonist nor-binaltorphimine 10 microM, but not the competitive NMDA receptor antagonist, DL-2-amino-5-phosphonovalerate (APV) 10 microM, significantly blocked the inhibitory effect of dynorphin A-(1-17) 0.1 microM on peak [Ca2+]i. However, APV 10 microM and nor-binaltorphimine 10 microM significantly antagonized the sustained rise in [Ca2+]i induced by a high concentration of dynorphin A-(1-17) 10 microM. Furthermore, in the presence, and following the addition, of increasing concentrations of dynorphin A-(1-17) (0.1, 1, 10 and 100 microM), the high concentrations of dynorphin A-(1-17) failed to produce a sustained rise in peak [Ca2+]i. These results suggested that dynorphin exerted a dualistic modulatory effect on [Ca2+]i in cultured rat spinal neurons, inducing a sustained and irreversible intracellular Ca2+ overload via activation of both NMDA and kappa-opioid receptors at higher concentrations, but inhibiting depolarization-evoked Ca2+ influx via kappa-opioid but not NMDA receptors at lower concentrations. Serial addition of graded concentrations of dynorphin A-(1-17) prevented the effect of high concentrations of dynorphin A-(1-17) on [Ca2+]i.

Animals↗

PubMed1998

A rapid method for combined laser scanning confocal microscopic and electron microscopic visualization of biocytin or neurobiotin-labeled neurons.

Intracellular recording and dye filling are widely used to correlate the morphology of a neuron with its physiology. With laser scanning confocal microscopy, the complex shapes of labeled neurons in three dimensions can be reconstructed rapidly, but this requires fluorescent dyes. These dyes are neither permanent nor electron dense and therefore do not allow investigation by electron microscopy. Here we report a technique that quickly and easily converts a fluorescent label into a more stable and electron-dense stain. With this technique, a neuron is filled with Neurobiotin or biocytin, reacted with fluorophore-conjugated avidin, and imaged by confocal microscopy. To permit long-term storage or EM study, the fluorescent label is then converted to a stable electron-dense material by a single-step conversion using a commercially available ABC kit. We find that the method, which apparently relies on recognition of avidin's excess biotin binding sites by the biotin-peroxidase conjugate, is both faster and less labor intensive than photo-oxidation procedures in common use. The technique is readily adaptable to immunocytochemistry with biotinylated probes, as we demonstrate using anti-serotonin as an example.

Animals↗

PubMed1997

The 60 kDa insulin receptor substrate functions like an IRS protein (pp60IRS3) in adipose cells.

The 60 kDa insulin receptor substrate in rat adipocytes that binds to the PI-3 kinase displays several functional characteristics in common with the IRS proteins; so we propose the name pp60(IRS3) to distinguish it from other tyrosine phosphorylated proteins of similar size. During insulin stimulation, p85 associated with pp60(IRS3) more rapidly than with IRS-1 or IRS-2. In mice lacking IRS-1, p85 associated more strongly with pp60(IRS3) than with IRS-2, suggesting that pp60(IRS3) provides an alternate pathway in these cells. Synthetic peptides containing two phosphorylated YMPM motifs displace pp60(IRS3) and IRS-1 from alphap85 immune complexes, suggesting that pp60(IRS3), like IRS-1, engages both SH2 domains in p85. Moreover, pp60(IRS3) binds to immobilized peptides containing a phosphorylated NPXY motif, suggesting that it contains a PTB domain with similar specificity to that in IRS-1. The cloning of pp60(IRS3) will reveal a new member of the IRS protein family which mediates insulin receptor signals in a narrow range of tissues.

Adipocytes↗

PubMed1997

Synaptic organization of the uniglomerular projection neurons of the antennal lobe of the moth Manduca sexta: a laser scanning confocal and electron microscopic study.

The detailed branching pattern and synaptic organization of the uniglomerular projection neurons of the antennal lobe, the first processing center of the olfactory pathway, of the moth Manduca sexta were studied with laser scanning confocal microscopy and a technique combining laser scanning confocal microscopy and electron microscopy. Uniglomerular projection neurons, identified electrophysiologically or morphologically, were stained intracellularly with neurobiotin or biocytin. Brains containing the injected neurons were treated with streptavidin-immunogold to label the injected material for electron microscopy and with Cy3-streptavidin to label the neurons with fluorescence for laser scanning confocal microscopy, and then embedded in Epon. Labeled neurons were imaged and reconstructed with laser scanning confocal microscopy (based on the retained fluorescence of the labeled neuron in the Epon block), and thin sections were cut at selected optical levels for correlation of light microscopic data and electron microscopic detail. Each neuron had a cell body in one of the three cell-body clusters of the antennal lobe, a primary neurite that extended across the coarse neuropil at the center of the antennal lobe and then formed a dense tuft of processes within a single glomerulus, and an axon that emanated from the primary neurite and projected from the antennal lobe via the antenno-cerebral tract to the lateral horn of the ipsilateral protocerebrum and, collaterally, to the calyces of the mushroom body. In the electron microscope, the fine dendritic branches in the apical zones of the glomeruli, where sensory axons terminate, were found to receive many input synapses. In deeper layers across the glomeruli, the processes participated in both input and output synapses, and the bases of the glomeruli, the most proximal, thickest branches formed output synapses. In both of the protocerebral areas in which axonal branches terminated, those branches formed exclusively output synapses. Our findings indicate that, in addition to conveying olfactory information to the protocerebrum, uniglomerular projection neurons in the antennal lobes of M. sexta participate in local intraglomerular synaptic circuitry.

Animals↗

PubMed1997

Organization of the antennal motor system in the sphinx moth Manduca sexta.

The antennae of the sphinx moth Manduca sexta are multimodal sense organs, each comprising three segments: scape, pedicel, and flagellum. Each antenna is moved by two systems of muscles, one controlling the movement of the scape and consisting of five muscles situated in the head capsule (extrinsic muscles), and the other system located within the scape (intrinsic muscles) and consisting of four muscles that move the pedicel. At least seven motoneurons innervate the extrinsic muscles, and at least five motoneurons innervate the intrinsic muscles. The dendritic fields of the antennal motoneurons overlap one another extensively and are located in the neuropil of the antennal mechanosensory and motor center. The density of motoneuronal arborizations is greatest in the lateral part of this neuropil region and decreases more medially. None of the motoneurons exhibits a contralateral projection. The cell bodies of motoneurons innervating the extrinsic muscles are distributed throughout an arching band of neuronal somata dorsal and dorsolateral to the neuropil of the antennal mechanosensory and motor center, whereas the cell bodies of motoneurons innervating the intrinsic muscles reside mainly among the neuronal somata situated dorsolateral to that neuropil.

Animals↗

PubMed1997

The IRS-2 gene on murine chromosome 8 encodes a unique signaling adapter for insulin and cytokine action.

Signal transduction by insulin and IGF-1, several interleukins (IL-2, IL-4, IL-9, IL-13), interferons, GH, and other cytokines involves IRS proteins, which link the receptors for these factors to signaling molecules with Src homology-2 domains (SH2-proteins). We recently reported the amino acid sequence of murine IRS-2; in order to examine a potential genetic role for this molecule in disease, we isolated the murine IRS-2 gene and compared the expression pattern of IRS-2 against IRS-1. Like IRS-1, IRS-2 is encoded by a single exon. Whereas IRS-1 is located on murine chromosome 1, IRS-2 is located on murine chromosome 8 near the insulin receptor. IRS-2 is expressed together with IRS-1 in many cells and tissues; however, IRS-2 predominates in murine hematopoietic cells where it may be essential for cytokine signaling; IRS-1 predominates in adipocytes and differentiated 3T3-L1 cells where it contributes to the normal insulin response. In 32D cells, IRS-1 and IRS-2 undergo differential tyrosine phosphorylation during insulin or IL-4 stimulation, as assessed indirectly by interaction with various recombinant SH2 domains. Thus, signaling specificity through the IRS proteins may be accomplished by specific expression patterns and distinct phosphorylation patterns during interaction with various activated receptors.

3T3 Cells↗

PubMed1996

Cross-talk between the insulin and angiotensin signaling systems.

Angiotensin II (AII), acting via its G-protein linked receptor, is an important regulator of cardiac, vascular, and renal function. Following injection of AII into rats, we find that there is also a rapid tyrosine phosphorylation of the major insulin receptor substrates 1 and 2 (IRS-1 and IRS-2) in the heart. This phenomenon appears to involve JAK2 tyrosine kinase, which associates with the AT1 receptor and IRS-1/IRS-2 after AII stimulation. AII-induced phosphorylation leads to binding of phosphatidylinositol 3-kinase (PI 3-kinase) to IRS-1 and IRS-2; however, in contrast to other ligands, AII injection results in an acute inhibition of both basal and insulin-stimulated PI 3-kinase activity. The latter occurs without any reduction in insulin receptor or IRS phosphorylation or in the interaction of the p85 and p110 subunits of PI 3-kinase with each other or with IRS-1/IRS-2. These effects of AII are inhibited by AT1 receptor antagonists. Thus, there is direct cross-talk between insulin and AII signaling pathways at the level of both tyrosine phosphorylation and PI 3-kinase activation. These interactions may play an important role in the association of insulin resistance, hypertension, and cardiovascular disease.

Angiotensin II↗

PubMed1996

Combining laser scanning confocal microscopy and electron microscopy in studies of the insect nervous system.

Experimentally determining the synaptic interconnections between neurons in the nervous system is laborious and difficult in any animal species, but especially so in many invertebrates, including insects, where neurons generally have large, finely branching neuritic trees that form both pre- and postsynaptic specializations in dense neuropils with other neuritic trees. Electron microscopy is needed to identify synapses, but correlation of synapse type and location with the overall branching patterns of neurons, which are visible readily only in the light microscope or through extensive reconstruction of serial electron-microscope sections, is very difficult. In this paper, we present a simple method that we have developed (Sun et al. (1995) J. Histochem. Cytochem., 43: 329-335) that combines laser scanning confocal microscopy and electron microscopy for the study of synaptic relationships of neurons in the antennal lobe, the first central neuropil in the olfactory pathway, of the moth Manduca sexta. Briefly, neurons are labeled by intracellular injection with neurobiotin or biocytin, and then processed with a gold-particle tag for electron microscopic study and a fluorescent tag for confocal microscopy, and embedded in plastic. The fluorescence of the labeled neuron in the plastic blocks is imaged in three dimensions with laser scanning confocal microscopy and then the neuron is thin-sectioned at precisely chosen depths for electron microscopic study. The fluorescence pattern can be monitored repeatedly between episodes of thin-sectioning, and subtraction of a fluorescence image from the previous fluorescence image reveals which fluorescent processes have been sectioned. In this way, electron microscopic detail can be mapped onto a three-dimensional light microscopic image of the neuron.

Animals↗

PubMed1996

The Fyn tyrosine kinase binds Irs-1 and forms a distinct signaling complex during insulin stimulation.

Irs-proteins link the receptors for insulin/IGF-1, growth hormones, and several interleukins and interferons to signaling proteins that contain Src homology-2 (SH2). To identify new Irs-1-binding proteins, we screened a mouse embryo expression library with recombinant [32P]Irs-1, which revealed a specific association between p59fyn and Irs-1. The SH2 domain in p59fyn bound to phosphorylated Tyr895 and Tyr1172, which are located in YXX(L/I) motifs. Mutation of p59fyn at the COOH-terminal tyrosine phosphorylation site (Tyr531) enhanced its binding to Irs-1 during insulin stimulation. Binding experiments with various SH2 protein revealed that Grb-2 was largely excluded from Irs-1 complexes containing p59fyn, whereas Grb-2 and p85 occurred in the same Irs-1 complex. By comparison with the insulin receptor, p59fyn kinase phosphorylated a unique cohort of tyrosine residues in Irs-1. These results outline a role for p59fyn or other related Src-kinases during insulin and cytokine signaling.

Amino Acid Sequence↗