Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:2.7.10.2 (focal adhesion kinase)
44,029 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We have reported two JAK-signaling modulators, CIS (cytokine-inducible SH2 protein) and JAB (JAK2 binding protein), which are structurally related. Here we cloned three additional CIS family genes (CIS2, CIS3, and CIS4) on the basis of an expression sequence tag (EST) database search. We also found at least two additional candidates of this gene family in the database. These genes were induced by erythropoietin and granulocyte-macrophage colony stimulating factor in certain hematopoietic cell lines. The SH2 domain and a C-terminal 40 amino acid region, designated the CIS homology domain (CH domain), are highly conserved in this family, while the N-terminal regions of these proteins share little similarity. A yeast two-hybrid assay and in vitro and in vivo binding assays revealed that in addition to JAB, CIS3 bound to the JAK2 tyrosine kinase domain (JH1), although the interaction of CIS3 with the JAK2-JH1 domain was much weaker than that of JAB. Transient expression of JAB and CIS3, but not other CISs, strongly inhibited leukemia inhibitory factor (LIF)-induced STAT3-reporter gene activation in 293 cells. Furthermore, constitutive overexpression of JAB and CIS3 in M1 leukemia cells prevented LIF-induced differentiation and growth arrest. Although the physiological function remains to be investigated, CIS family genes could play a role in the negative regulation of cytokine signaling by interacting with specific targets.
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PMID:Cloning and characterization of novel CIS family genes. 934 48

The ability of five members of the cytokine-inducible SH2 protein family (CIS1-4) and JAK2 binding (JAB) protein to affect prolactin receptor (PRLR)-mediated activity was tested in human 293 embryonic kidney fibroblasts transiently transfected with rat PRLR, five concentrations of CIS/JAB Myc-tagged cDNAs and a STAT5-responsive reporter gene encoding luciferase. The protein expressions of CIS1, CIS2, CIS3 and JAB were comparable, whereas the level of CIS4 was slightly lower. PRLR-mediated luciferase activity was abolished in a dose-dependent manner in cells transfected with cDNA of CIS3 or JAB, even at concentrations below the level of protein detection by anti-Myc antibody. In contrast, CIS1, CIS2 and CIS4 had little or no effect, despite similar levels of expression. CIS1 expression in postpartum mouse mammary glands was high and changed little in the course of 3 days. CIS2 and CIS3 expression was also high and increased further, whereas JAB expression was very low. These results hint that at least in mammary gland CIS3 is likely the main physiological negative regulator of the PRLR-mediated JAK2/STAT5 pathway.
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PMID:Cytokine-inducible SH2 protein (CIS3) and JAK2 binding protein (JAB) abolish prolactin receptor-mediated STAT5 signaling. 988 1

IL-4 is an important regulator of the activation, proliferation, and differentiation of many hematopoetic cells. Many of these biological effects result from the activation of Janus kinases (JAK)1 and JAK3 and the transcription factor Stat6. Recent data suggest that members of the SOCS (suppressor of cytokine signaling) family of proteins can inhibit JAK-STAT signaling. We have examined the ability of SOCS family members to suppress IL-4 signaling, and we have found that SOCS-1 potently inhibits the activation of JAK1 kinase and Stat6 in response to IL-4. Furthermore, SOCS-1 can inhibit the induction of CD23 expression by IL-4. SOCS-2 does not inhibit induction of signaling by IL-4, while inhibition of IL-4 signaling by SOCS-3 can be detected in transient transfection systems, but not in stable cell lines. These studies implicate SOCS-1 in modulation of IL-4 signaling and suggest that SOCS-1 may play a role in regulating the immune response.
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PMID:Cutting edge: SOCS-1 is a potent inhibitor of IL-4 signal transduction. 1020 92

Prolactin (PRL) has been shown to activate the cytoplasmic tyrosine kinase Janus kinase 2 (Jak2) and the subsequent recruitment of various signaling molecules including members of the signal transducer and activator of transcription family of transcription factors. Recently, an expanding family of cytokine-inducible inhibitors of signaling has been identified that initially included four members: suppressor of cytokine signaling (SOCS)-1, SOCS-2, SOCS-3, and cytokine-inducible src homology domain 2 (SH-2) proteins. The present study analyzes the role of these members in PRL signaling. Constitutive expression of SOCS-1 and SOCS-3 suppressed PRL-induced signal transducer and activator of transcription 5-dependent gene transcription, and Jak2 tyrosine kinase activity was greatly reduced in the presence of SOCS-1 or SOCS-3. SOCS-1 was shown to associate with Jak2, whereas SOCS-2 was associated with the prolactin receptor. Co-transfection studies were conducted to further analyze the interactions of SOCS proteins. SOCS-2 was shown to suppress the inhibitory effect of SOCS-1 by restoring Jak2 kinase activity but did not affect the inhibitory effect of SOCS-3 on PRL signaling. Northern blot analysis revealed that SOCS-3 and SOCS-1 genes were transiently expressed in response to PRL, both in vivo and in vitro, whereas the expression of SOCS-2 and CIS genes was still elevated 24 h after hormonal stimulation. We thus propose that the early expressed SOCS genes (SOCS-1 and SOCS-3) switch off PRL signaling and that the later expressed SOCS-2 gene can restore the sensitivity of cells to PRL, partly by suppressing the SOCS-1 inhibitory effect.
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PMID:Inhibition and restoration of prolactin signal transduction by suppressors of cytokine signaling. 1045 12

We earlier demonstrated that leptin induces expression of SOCS-3 mRNA in the hypothalamus. Furthermore, transfection data suggest that SOCS-3 is an inhibitor of leptin signaling. However, little is known about the regulation of SOCS-3 expression by leptin and the mechanism by which SOCS-3 inhibits leptin action. We here show that in CHO cells stably expressing the long form of the leptin receptor (CHO-OBRl), leptin induces transient expression of endogenous SOCS-3 mRNA but not of CIS, SOCS-1, or SOCS-2 mRNA. SOCS-3 protein levels were maximal after 2-3 h of leptin treatment and remained elevated at 20 h. Furthermore, in leptin-pretreated CHO-OBRl cells, proximal leptin signaling was blocked for more than 20 h after pretreatment, thus correlating with increased SOCS-3 expression. Leptin pretreatment did not affect cell surface expression of leptin receptors as measured by (125)I-leptin binding assays. In transfected COS cells, forced expression of SOCS-3 results in inhibition of leptin-induced tyrosine phosphorylation of JAK2. Finally, JAK2 co-immunoprecipitates with SOCS-3 in lysates from leptin-treated COS cells. These results suggest that SOCS-3 is a leptin-regulated inhibitor of proximal leptin signaling in vivo. Excessive SOCS-3 activity in leptin-responsive cells is therefore a potential mechanism for leptin resistance, a characteristic feature in human obesity.
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PMID:The role of SOCS-3 in leptin signaling and leptin resistance. 1051 92

In this study we have investigated the role of suppressor of cytokine signaling (SOCS) proteins in GH receptor-mediated signaling. GH-induced transcription was inhibited by SOCS-1 and SOCS-3, while SOCS-2 and cytokine inducible SH2-containing protein (CIS) had no effect By using chimeric SOCS proteins it was found that the ability of SOCS proteins to inhibit GH-mediated transcription was located in the amino-terminal 40-80 amino acids. In SOCS-3, 46 amino acids C-terminal to the SH2 domain were required for the inhibitory activity, while a truncated SOCS-1 having only 2 amino acids C-terminal to the SH2 domain was able to inhibit GH-mediated transcription. Both SOCS-1 and SOCS-3 were able to inhibit GH-induced STAT5 (signal transducer and activator of transcription) activation. SOCS-1 inhibited the tyrosine kinase activity of Janus kinase 2 (JAK2) directly, while SOCS-3 only inhibited JAK2 when stimulated by the GH receptor. All four SOCS proteins were able to bind to a tyrosine-phosphorylated glutathione-S-transferase-GH receptor fusion protein, and SOCS-3 required the same 46 C-terminal amino acids for GH receptor binding as it did for inhibition of GH-mediated transcription and STAT5 activation. These data suggest that SOCS-1 and -3 can suppress GH-induced transcriptional activity, presumably by inhibiting the kinase activity of JAK2 either directly in the case of SOCS-1 or via binding to the tyrosine-phosphorylated GH receptor in the case of SOCS-3.
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PMID:Mechanism of inhibition of growth hormone receptor signaling by suppressor of cytokine signaling proteins. 1055 77

The inhibition of growth hormone (GH) signaling by five members of the GH-inducible suppressor of cytokine signaling (SOCS/CIS) family was investigated in transfected COS cells. Complete inhibition of GH activation of the signal transducer STAT5b and STAT5b-dependent transcriptional activity was observed upon expression of SOCS-1 or SOCS-3, while partial inhibition (CIS, SOCS-2) or no inhibition (SOCS-6) was seen with other SOCS/CIS family members. SOCS-1, SOCS-2, SOCS-3, and CIS each strongly inhibited the GH receptor (GHR)-dependent tyrosine phosphorylation of JAK2 seen at low levels of transfected JAK2; however, only SOCS-1 strongly inhibited the GHR-independent tyrosine phosphorylation of JAK2 seen at higher JAK2 levels. To probe for interactions with GHR, in vitro binding assays were carried out using glutathione S-transferase-GHR fusion proteins containing variable lengths of GHR's COOH-terminal cytoplasmic domain. CIS and SOCS-2 bound to fusions containing as few as 80 COOH-terminal GHR residues, provided the fusion protein was tyrosine-phosphorylated. By contrast, SOCS-3 binding required tyrosine-phosphorylated GHR membrane-proximal sequences, SOCS-1 binding was tyrosine phosphorylation-independent, and SOCS-6 did not bind the GHR fusion proteins at all. Mutation of GHR's membrane-proximal tyrosine residues 333 and 338 to phenylalanine suppressed the inhibition by SOCS-3, but not by CIS, of GH signaling to STAT5b. SOCS/CIS proteins can thus inhibit GH signaling to STAT5b by three distinct mechanisms, distinguished by their molecular targets within the GHR-JAK2 signaling complex, as exemplified by SOCS-1 (direct JAK2 kinase inhibition), SOCS-3 (inhibition of JAK2 signaling via membrane-proximal GHR tyrosines 333 and 338), and CIS and SOCS-2 (inhibition via membrane-distal tyrosine(s)).
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PMID:SOCS/CIS protein inhibition of growth hormone-stimulated STAT5 signaling by multiple mechanisms. 1058 30

Suppressor of cytokine signaling (SOCS) family proteins were originally identified as cytokine-induced negative regulators of cytokine signaling. We show that SOCS-1 and SOCS-3 inhibit interleukin (IL)-4-dependent signal transducer and activator of transcription 6 (Stat6) activation of and subsequent gene induction. By contrast, SOCS-2 and cytokine-inducible Src homology domain 2 (SH2)-containing protein up-regulate these processes. IL-4 initiates transmembrane signaling through two types of receptor complexes comprising the IL-4Ralpha subunit and the associated Janus kinase 1 (Jak1) as common essential components. We demonstrate that both SOCS-1- and SOCS-3-mediated down-regulation of IL-4 signaling is due to an inhibition of the receptor associated Jak1 activity. The SOCS proteins contain an amino-terminal region of variable length and primary structure, a central SH2 domain, and a carboxyl-terminal conserved motif termed SOCS-box. We show that the SH2 domains of SOCS-2, SOCS-3, and cytokine-inducible SH2-containing protein are functionally redundant in regulating the IL-4-dependent Jak-Stat signaling. The Pre-SH2 domains of SOCS-2 and SOCS-3 confer the specificity of their regulatory function. Importantly, the Pre-SH2 domain of SOCS-3 alone can inhibit IL-4 signaling. The SH2-proximal 25 amino acids of SOCS-3 are sufficient for this inhibition, and the Thr residue at position 24 and the Phe residue at position 25 are individually indispensable for its inhibitory function. Thus, the Thr-Phe motif in the Pre-SH2 domain plays a critical role in SOCS-3-mediated inhibition of the IL-4-dependent Jak-Stat signaling, likely by regulating the mode of SOCS-Jak interaction.
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PMID:Identification of critical residues required for suppressor of cytokine signaling-specific regulation of interleukin-4 signaling. 1095 Sep 67

Chronic renal failure (CRF) is associated with resistance to the growth-promoting and anabolic actions of growth hormone (GH). In rats with CRF induced by partial renal ablation, 7 days of GH treatment had a diminished effect on weight gain and hepatic IGF-1 and IGFBP-1 mRNA levels, compared with sham-operated pair-fed controls. To assess whether GH resistance might be due to altered signal transduction, activation of the JAK-STAT pathway was studied 10 or 15 minutes after intravenous injection of 5 mg/kg GH or vehicle. Hepatic GH receptor (GHR) mRNA levels were significantly decreased in CRF, but GHR protein abundance and GH binding to microsomal and plasma membranes was unaltered. JAK2, STAT1, STAT3, and STAT5 protein abundance was also unchanged. However, GH-induced tyrosine phosphorylation of JAK2, STAT5, and STAT3 was 75% lower in the CRF animals. Phosphorylated STAT5 and STAT3 were also diminished in nuclear extracts. The expression of the suppressor of cytokine signaling-2 (SOCS-2) was increased twofold in GH-treated CRF animals, and SOCS-3 mRNA levels were elevated by 60% in CRF, independent of GH treatment. In conclusion, CRF causes a postreceptor defect in GH signal transduction characterized by impaired phosphorylation and nuclear translocation of GH-activated STAT proteins, which is possibly mediated, at least in part, by overexpression of SOCS proteins.
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PMID:Impaired JAK-STAT signal transduction contributes to growth hormone resistance in chronic uremia. 1148 40

GH is required for normal postnatal growth and metabolism. GH stimulates postnatal growth through induction of IGF-I gene expression. Although the liver is the major site of GH-regulated IGF-I, recent evidence indicates that GH-regulated IGF-I expression in nonhepatic tissues is sufficient for normal postnatal growth. One potentially important nonhepatic site of GH-stimulated IGF-I expression is skeletal muscle, as injection of GH into animals leads to increased IGF-I mRNA in this tissue. Nevertheless, direct effects of GH in skeletal muscle cells in culture have not been reported. We therefore tested the C2C12 myogenic cell line for its response to GH and demonstrate that C2C12 skeletal muscle cells rapidly respond to physiological levels of GH with increased tyrosine phosphorylation of the GH receptor, Janus kinase 2, signal transducer and activator of transcription-5a and -5b, insulin receptor substrate-1, and activation of MAPKs/ERKs and protein kinase B/Akt. In these cells, GH stimulates the expression of IGF-I and two members of the suppressors of cytokine signaling family, cytokine-inducible SH2-containing protein and suppressor of cytokine signaling-2. Treatment of C2C12 myoblasts with either the MAPK kinase inhibitor PD98059 or the PI3K inhibitor wortmannin results in higher levels of GH-induced IGF-I and suppressor of cytokine signaling-2 mRNA expression, suggesting that activation of MAPK and PI3K pathways has an inhibitory role in IGF-I and suppressor of cytokine signaling-2 gene regulation. Therefore, C2C12 cells provide the first in vitro model system to study various aspects of GH action in skeletal muscle.
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PMID:GH regulation of IGF-I and suppressor of cytokine signaling gene expression in C2C12 skeletal muscle cells. 1151 67


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