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B J Goldstein

Publications and source records attributed to B J Goldstein.

At least 73 records · Page 4Linked to original sources
PubMed1994

Insulin receptor substrate-1 (IRS-1) expression in rat brain.

IRS-1 is phosphorylated on tyrosine residues after insulin stimulation and participates in the early events of signal transduction in peripheral insulin-sensitive tissues. This study determined whether neuronal populations in the rat olfactory bulb and hippocampus (brain regions which have very high concentrations of insulin receptors) also express IRS-1 and contain phosphotyrosine, using in situ hybridization, receptor binding, and immunocytochemistry. IRS-1 mRNA was colocalized with insulin receptor mRNA in neuron cell bodies of hippocampus and olfactory bulb. Similarly, IRS-1 immunoreactivity in hippocampus and olfactory bulb was concentrated in layers that contain synapses of these neurons and have both high insulin binding and phosphotyrosine levels. Thus, IRS-1 and insulin receptors are coexpressed in discrete populations of neurons, suggesting a signal transduction mechanism by which insulin may influence metabolism and gene expression in the brain.

Animals↗
PubMed1993

Regenerative proliferation in inner ear sensory epithelia from adult guinea pigs and humans.

Supporting cells in the vestibular sensory epithelia from the ears of mature guinea pigs and adult humans proliferate in vitro after treatments with aminoglycoside antibiotics that cause sensory hair cells to die. After 4 weeks in culture, the epithelia contained new cells with some characteristics of immature hair cells. These findings are in contrast to expectations based on previous studies, which had suggested that hair cell loss is irreversible in mammals. The loss of hair cells is responsible for hearing and balance deficits that affect millions of people.

Adult↗
PubMed1993

Modulation of expression of insulin and IGF-I receptor by Epstein-Barr virus and its gene products LMP and EBNA-2 in lymphocyte cell lines.

The receptors for insulin and insulin-like growth factor I (IGF-I) are two closely related integral membrane glycoproteins involved in signalling of cell growth and metabolism. We have used the unique paradigm of pairs of Burkitt lymphoma cell lines (BLO2, BL30, BL41) with or without Epstein-Barr Virus (EBV) infection and cells transfected with EBV-related genes to examine effects of EBV on expression of these receptors at the gene and protein functional level. In BL30 and BL41 cells, EBV infection increased surface insulin binding and total receptor number by 2- and 18-fold, respectively. By contrast, EBV infection decreased total IGF-I receptors by 29 to 87% in all three cell lines. In general, there was a correlation between total receptor concentration and the level of insulin or IGF-I receptor mRNAs, although in one cell line insulin binding increased while receptor mRNA levels decreased slightly, suggesting posttranslational effects. BL41 cells transfected with a vector expressing the EBV latent membrane protein (LMP) exhibited a 2.6- to 3.2-fold increase in insulin receptor expression, whereas cells transfected with EBNA-2 (one of the EBV nuclear antigens) alone exhibited no effect. However, EBNA-2 appears to be required for the EBV effect on insulin receptor expression since cells infected with a mutant virus, P3JHRI, which lacks the EBNA-2 gene failed to show an increase in insulin receptor number. These data indicate that EBV infection of lymphocytes increases expression of insulin receptors while simultaneously decreasing expression of IGF-I receptors. The magnitude and sometimes even the direction of change, depends on host cell factors. A maximal increase in insulin receptors appears to require the coordinate action of several of the EBV proteins including LMP and EBNA-2.

Antigens, Viral↗
PubMed1993

Regulation of insulin receptor signaling by protein-tyrosine dephosphorylation.

Protein-tyrosine phosphatases (PTPases) that dephosphorylate the active (autophosphorylated) form of the insulin receptor and attenuate its tyrosine kinase activity play an essential regulatory role in signaling mediated by the insulin receptor. PTPases also modulate signaling through postreceptor pathways by catalyzing the dephosphorylation of cellular substrates of the insulin receptor kinase, such as IRS-1, or other tyrosine-phosphorylated proteins along the cellular cascade of insulin action. Recent studies have provided important data regarding PTPase(s) in insulin-responsive tissues that may regulate various components of the insulin action pathway. Further studies in this area will enhance our understanding of the mechanisms involved in insulin signaling and clarify the potential involvement of PTPases in the pathophysiology of insulin-resistant disease states.

Protein Tyrosine Phosphatases↗
PubMed1992

Differential regulation of mRNAs encoding three protein-tyrosine phosphatases by insulin and activation of protein kinase C.

Protein-tyrosine phosphatases (PTPases) play an essential role in the control of signalling through phosphotyrosine pathways. Since little is known about the regulation of these enzymes, we examined the effect of insulin and phorbol 12-myristate 13-acetate (PMA) treatment of well-differentiated rat hepatoma (Fao) cells on the expression of mRNAs encoding three major PTPase homologs in liver: PTPase1B, an intracellular enzyme with a single conserved PTPase domain, and two tandem-domain, transmembrane PTPases, known as LAR and LRP. Treatment of serum-deprived cells with 100 nM insulin increased the abundance of the 4.3 kb and 1.6 kb mRNAs encoding PTPase1B on Northern analysis by 1.6 and 3.1-fold, respectively (p < or = 0.02). Similarly, exposure to 100 ng/ml PMA increased the 4.3 and 1.6 kb PTPase1B mRNAs by 4.5 and 5.7-fold, respectively (p < or = 0.035). In contrast, treatment with insulin or PMA had no significant effect of the abundance of mRNA encoding either LAR or LRP. PMA appeared to have a transcriptional effect on the PTPase1B gene by a protein kinase C-mediated mechanism. The increase in PTPase1B mRNA expression by insulin and PMA suggests that this PTPase may provide feed-back regulation of signalling through the insulin action pathway as well as a potential link between the action of protein kinase C and the regulation of specific phosphotyrosine residues in cells.

Animals↗
PubMed1992

Insulin receptor protein-tyrosine phosphatases. Leukocyte common antigen-related phosphatase rapidly deactivates the insulin receptor kinase by preferential dephosphorylation of the receptor regulatory domain.

A number of protein-tyrosine phosphatase(s) (PTPases) have been shown to dephosphorylate the insulin receptor in vitro; however, it is not known whether any individual PTPase has specificity for certain phosphotyrosine residues of the receptor that regulate its intrinsic tyrosine kinase activity. We evaluated the deactivation of the insulin receptor kinase by three candidate enzymes that are expressed in insulin-sensitive rat tissues, including the receptor-like PTPases LAR and LRP, and the intracellular enzyme, PTPase1B. Purified insulin receptors were activated by insulin and receptor dephosphorylation, and kinase activity was quantitated after incubation with recombinant PTPases from an Escherichia coli expression system. When related to the level of overall receptor dephosphorylation, LAR deactivated the receptor kinase 3.1 and 2.1 times more rapidly than either PTPase1B or LRP, respectively (p less than 0.03). To assess whether these effects were associated with preferential dephosphorylation of the regulatory (Tyr-1150) domain of the receptor beta-subunit, we performed tryptic mapping of the insulin receptor beta-subunit after dephosphorylation by PTPases. Relative to the rate of initial loss of 32P from receptor C-terminal sites, LAR dephosphorylated the Tris-phosphorylated Tyr-1150 domain 3.5 and 3.7 times more rapidly than either PTPase1B or LRP, respectively (p less than 0.01). The accelerated deactivation of the insulin receptor kinase by LAR and its relative preference for regulatory phosphotyrosine residues further support a potential role for this transmembrane PTPase in the physiological regulation of insulin receptors in intact cells.

Animals↗
PubMed1992

Insulin receptor and epidermal growth factor receptor dephosphorylation by three major rat liver protein-tyrosine phosphatases expressed in a recombinant bacterial system.

Protein-tyrosine phosphatases (PTPases) play an essential role in the regulation of signal transduction mediated by reversible protein-tyrosine phosphorylation. In order to characterize individual rat hepatic PTPases that might have specificity for autophosphorylated receptor tyrosine kinases, we isolated cDNA segments encoding three PTPases (PTPase 1B, LAR and LRP) that are expressed in insulin-sensitive liver and skeletal muscle tissue, and evaluated their catalytic activity in vitro. The intrinsic PTPase activities of the full-length PTPase 1B protein and the cytoplasmic domains of LAR and LRP were studied by expression of recombinant cDNA constructs in the inducible bacterial vector pKK233-2 using extracts of a host strain of Escherichia coli that lacks endogenous PTPase activity. Each of the cloned cDNAs dephosphorylated a cognate phosphopeptide derived from the regulatory region of the insulin receptor. Despite having only 30-39% sequence identity in their catalytic domains, LAR and PTPase 1B had similar relative activities between the peptide substrate and intact insulin receptors, and also displayed similar initial rates of simultaneous dephosphorylation of insulin and epidermal growth factor (EGF) receptors. In contrast, LRP exhibited a higher rate of dephosphorylation of both intact receptors relative to the peptide substrate, and also dephosphorylated EGF receptors more rapidly than insulin receptors. These studies indicate that three PTPases with markedly divergent structures have the catalytic potential to dephosphorylate both insulin and EGF receptors in intact cells and that redundant PTPase activity may occur in vivo. For these PTPases to have specific physiological actions in intact cells, they must be influenced by steric effects of the additional protein segments of the native transmembrane enzymes, cellular compartmentalization and/or interactions with regulatory proteins.

Amino Acid Sequence↗
PubMed1992

Approaches to the molecular cloning of protein-tyrosine phosphatases in insulin-sensitive tissues.

The intrinsic tyrosyl kinase activity of the insulin receptor is regulated by a balance between insulin-induced receptor autophosphorylation, which stimulates the receptor kinase, and enzymatic dephosphorylation of the receptor, which deactivates its kinase activity. The cellular protein-tyrosine phosphatase (PTPase) enzymes responsible for reversing the activated state of the insulin receptor have not been characterized. Our laboratory is interested in identifying and cloning the specific PTPase(s) that regulate the phosphorylation state of the insulin receptor. This chapter will summarize the design and results of our initial molecular cloning studies to identify specific PTPases in insulin-sensitive tissues that may have a potential physiological role in insulin action and clinical insulin resistance.

Amino Acid Sequence↗
PubMed1992

Protein-tyrosine phosphatases and the regulation of insulin action.

Protein-tyrosine phosphatases (PTPases) play an important role in the regulation of insulin action by dephosphorylating the active (autophosphorylated) form of the insulin receptor and attenuating its tyrosine kinase activity. PTPases can also modulate post-receptor signalling by catalyzing the dephosphorylation of cellular substrates of the insulin receptor kinase. Dramatic advances have recently been made in our understanding of PTPases as an extensive family of transmembrane and intracellular proteins that are involved in a number of pathways of cellular signal transduction. Identification of the PTPase(s) which act on various components of the insulin action cascade will not only enhance our understanding of insulin signalling but will also clarify the potential involvement of PTPases in the pathophysiology of insulin-resistant disease states. This brief review provides a summary of reversible tyrosine phosphorylation events in insulin action and available data on candidate PTPases in liver and skeletal muscle that may be involved in the regulation of insulin action.

Animals↗
PubMed1992

POEMS syndrome with myocardial infarction: observations concerning pathogenesis and review of the literature.

A 27-year-old white man with no significant risk factors for coronary artery disease presented with a 9-month history of progressive impotence, gynecomastia, lower extremity paresthesias, and extensive myocardial infarction and subsequently developed ulcerative proctitis. A diagnosis of POEMS syndrome was made based on the clinical presentation; additional physical findings of papilledema, clubbing, and hyperpigmentation; and laboratory findings of an immunoglobulin G M component of the lambda subtype, elevated cerebrospinal fluid protein, and typical sclerotic bone lesions. Abnormal in vitro binding of the patient's serum immunoglobulin to testicular tissue was also seen. Cardiac catheterization showed evidence of diffuse coronary artery narrowing and left ventricular wall motion abnormalities. Diffuse coronary involvement and ulcerative proctitis have not been previously described in POEMS syndrome. It is hypothesized that an abnormal immunoglobin (or fragment) is responsible for both findings. Furthermore, the detection of antitesticular autoantibodies suggests the possibility of an interaction between the antibody and Leydig cells, leading to an alteration in the synthesis and release of sex steroids and thereby explaining the gonadal failure seen in this syndrome. Long-term glucocorticoid therapy for the past 5 years has resulted in marked subjective and objective improvement.

Adult↗
PubMed1992

Heterogeneity of messenger RNA that encodes the rat insulin receptor is limited to the domain of exon 11. Analysis by RNA heteroduplex mapping, amplification of cDNA, and in vitro translation.

Structural isoforms of the insulin receptor that occur in various tissues have been postulated to be involved in certain actions of insulin in target cells. To determine whether these insulin-receptor subtypes are caused by alterations in the receptor primary structure, we used RNA heteroduplex mapping and amplification of cDNA to detect variation in the coding region of insulin-receptor mRNA from 5 rat tissues. A complete series of overlapping antisense [32P]RNA probes was prepared from plasmids containing segments of a full-length rat insulin-receptor cDNA, and probes were hybridized individually in solution with polyadenylated RNA from rat brain, kidney, liver, skeletal muscle, and spleen. After ribonuclease digestion, probe fragments were analyzed by denaturing gel electrophoresis. Tissue-specific cleavage of the mRNA:RNA probe heteroduplex, attributable to sequence mismatch, was detected only for a single probe covering the distal alpha-subunit, as expected for the known alternative splicing of rat insulin-receptor mRNA in this region. No evidence for additional heterogeneity of the receptor mRNA coding region was observed in the 5 tissues studied either by RNA heteroduplex mapping or, in some areas, by regional amplification of insulin-receptor cDNA. Cell-free translation of size-fractionated polyadenylated RNA was used to further demonstrate that each of the major insulin-receptor mRNA size classes in rat liver contained both forms of the alternatively spliced mRNA transcripts and produced two insulin-proreceptor polypeptides. These results suggest that heterogeneity of the insulin-receptor mRNA coding region affecting the receptor primary structure is limited to the distal alpha-subunit near the subunit cleavage site.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

Identification of skeletal muscle protein-tyrosine phosphatases by amplification of conserved cDNA sequences.

Specific protein-tyrosine phosphatase (PTPase) enzymes that regulate signal transduction by the insulin receptor in target tissues have not been identified. We evaluated the expression of PTPase homologs in skeletal muscle since this tissue is the major site of insulin-mediated glucose disposal in vivo. A rat skeletal muscle cDNA pool was prepared with a set of degenerate oligonucleotide primers and PTPase cDNA sequences were amplified using pairs of "guess-mers" that were deduced from highly conserved residues within the known catalytic domains of these enzymes. Sequences encoding three "receptor-like" transmembrane PTPases were identified and two of these (known as LAR and LRP) were confirmed to be expressed in muscle by subsequent cDNA library screening and Northern blot analysis. The expression of the LAR and LRP PTPases in skeletal muscle suggests that these enzymes might have a role in the regulation of insulin action in muscle and other insulin-sensitive tissues.

Amino Acid Sequence↗
PubMed1991

Structure of the insulin receptor substrate IRS-1 defines a unique signal transduction protein.

Since the discovery of insulin nearly 70 years ago, there has been no problem more fundamental to diabetes research than understanding how insulin works at the cellular level. Insulin binds to the alpha subunit of the insulin receptor which activates the tyrosine kinase in the beta subunit, but the molecular events linking the receptor kinase to insulin-sensitive enzymes and transport processes are unknown. Our discovery that insulin stimulates tyrosine phosphorylation of a protein of relative molecular mass between 165,000 and 185,000, collectively called pp185, showed that the insulin receptor kinase has specific cellular substrates. The pp185 is a minor cytoplasmic phosphoprotein found in most cells and tissues; its phosphorylation is decreased in cells expressing mutant receptors defective in signalling. We have now cloned IRS-1, which encodes a component of the pp185 band. IRS-1 contains over ten potential tyrosine phosphorylation sites, six of which are in Tyr-Met-X-Met motifs. During insulin stimulation, the IRS-1 protein undergoes tyrosine phosphorylation and binds phosphatidylinositol 3-kinase, suggesting that IRS-1 acts as a multisite 'docking' protein to bind signal-transducing molecules containing Src-homology 2 and Src-homology-3 domains. Thus IRS-1 may link the insulin receptor kinase and enzymes regulating cellular growth and metabolism.

Animals↗
PubMed1990

The rat insulin receptor: primary structure and conservation of tissue-specific alternative messenger RNA splicing.

To investigate whether alterations in the polypeptide structure of the insulin receptor might explain the heterogeneity observed in its properties between species and in different tissues, we obtained the complete primary structure of the rat liver insulin receptor precursor by cDNA cloning and sequencing. The rat proreceptor contains 1357 amino acids and has 95.2% identity with deduced polypeptide sequences reported for the human insulin receptor precursor. In addition, the rat liver insulin receptor cDNA was similar to the form of the human insulin receptor mRNA that contains Exon 11 in its coding region, which undergoes tissue-specific alternative splicing. Using the polymerase chain reaction to amplify a cDNA segment corresponding to this region in several rat tissues, the splicing pattern of sequences homologous to Exon 11 was found to be highly conserved, providing further evidence that these two forms of the insulin receptor may serve important functional or regulatory roles. These studies have also identified subtle variations in the primary structure of the insulin receptor which may influence its properties between species.

Amino Acid Sequence↗