52 research outputs found
Novel anticancer agents based on targeting the trimer interface of the PRL phosphatase
PRL oncoproteins are phosphatases overexpressed in numerous types of human cancer. Elevated levels of PRL associate with metastasis and poor clinical outcomes. In principle, PRL phosphatases offer appealing therapeutic targets, but they remain underexplored due to the lack of specific chemical probes. In this study, we address this issue by exploiting a unique property of PRL phosphatases, namely, that they may function as homotrimers. Starting from a sequential structure-based virtual screening and medicinal chemistry strategy, we identified Cmpd-43 and several analogs which disrupt PRL1 trimerization. Biochemical and structural analyses demonstrate that Cmpd-43 and its close analogs directly bind the PRL1 trimer interface and obstruct PRL1 trimerization. Cmpd-43 also specifically blocks the PRL1-induced cell proliferation and migration through attenuation of both ERK1/2 and Akt activity. Importantly, Cmpd-43 exerted potent anticancer activity both in vitro and in vivo in a murine xenograft model of melanoma. Our results validate a trimerization-dependent signaling mechanism for PRL and offer proof-of-concept for trimerization inhibitors as candidate therapeutics to treat PRL-driven cancer
Molecular Basis of Gain-of-Function LEOPARD Syndrome-Associated SHP2 Mutations
The Src homology 2 (SH2) domain-containing
protein tyrosine phosphatase
2 (SHP2) is a critical signal transducer downstream of growth factors
that promotes the activation of the RAS-ERK1/2 cascade. In its basal
state, SHP2 exists in an autoinhibited closed conformation because
of an intramolecular interaction between its N-SH2 and protein tyrosine
phosphatase (PTP) domains. Binding to pTyr ligands present on growth
factor receptors and adaptor proteins with its N-SH2 domain localizes
SHP2 to its substrates and frees the active site from allosteric inhibition.
Germline mutations in SHP2 are known to cause both Noonan syndrome
(NS) and LEOPARD syndrome (LS), two clinically similar autosomal dominant
developmental disorders. NS-associated SHP2 mutants display elevated
phosphatase activity, while LS-associated SHP2 mutants exhibit reduced
catalytic activity. A conundrum in how clinically similar diseases
result from mutations to SHP2 that have opposite effects on this enzyme’s
catalytic functionality exists. Here we report a comprehensive investigation
of the kinetic, structural, dynamic, and biochemical signaling properties
of the wild type as well as all reported LS-associated SHP2 mutants.
The results reveal that LS-causing mutations not only affect SHP2
phosphatase activity but also induce a weakening of the intramolecular
interaction between the N-SH2 and PTP domains, leading to mutants
that are more readily activated by competing pTyr ligands. Our data
also indicate that the residual phosphatase activity associated with
the LS SHP2 mutant is required for enhanced ERK1/2 activation. Consequently,
catalytically impaired SHP2 mutants could display gain-of-function
properties because of their ability to localize to the vicinity of
substrates for longer periods of time, thereby affording the opportunity
for prolonged substrate turnover and sustained RAS-ERK1/2 activation
Dissociative Phosphoryl Transfer in PEP Mutase Catalysis: Structure of the Enzyme/Sulfopyruvate Complex and Kinetic Properties of Mutants â€
Crystal Structures of 2-Methylisocitrate Lyase in Complex with Product and with Isocitrate Inhibitor Provide Insight into Lyase Substrate Specificity, Catalysis and Evolution â€
Conformational flexibility of PEP mutase
ABSTRACT: Previous work has indicated that PEP mutase catalyzes the rearrangement of phosphoenolpyruvate to phosphonopyruvate by a dissociative mechanism. The crystal structure of the mutase with Mg(II) and sulfopyruvate (a phosphonopyruvate analogue) bound showed that the substrate is anchored to the active site by the Mg(II), and shielded from solvent by a large loop (residues 115-133). Here, the crystal structures of wild-type and D58A mutases, in the apo state and in complex with Mg(II), are reported. In both unbound and Mg(II)-bound states, the active site is accessible to the solvent. The loop (residues 115-133), which in the enzyme-inhibitor complexes covers the active site cavity, is partially disordered or adopts a conformation that allows access to the cavity. In the apo state, the residues associated with Mg(II) binding are poised to accept the metal ion. When Mg(II) binds, the coordination is the same as that previously observed in the enzyme-Mg(II) sulfopyruvate complex, except that the coordination positions occupied by two ligand oxygen atoms are occupied by two water molecules. When the loop opens, three key active site residues are displaced from the active site, Lys120, Asn122, and Leu124. Lys120 mediates Mg(II) coordination. Asn122 and Leu124 surround the transferring phosphoryl group, and thus prevent substrate hydrolysis. Amino acid replacement of any one of these three loop residues results in a significant loss of catalytic activity. It is hypothesized that the loop serves to gate the mutas
Changes in the Anatomic and Microscopic Structure and the Expression of HIF-1α and VEGF of the Yak Heart with Aging and Hypoxia - Fig 3
<p>A: The diameter of collagen fiber. B: The optical density of collagen fiber.</p
HIF-1α and VEGF protein expression in the yak heart were measured by ELISA.
<p>A: HIF-1α expression. B: VEGF expression.</p
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