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

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

Enzymatic activities of Complex I-V of mitochondria.

<p>Unit: nmoles/min/mg protein.</p

Age-related changes in the morphology and the distribution of IgA and IgG in the palatine tonsils of yaks (Bos grunniens)

This study aimed to describe the age-related morphological changes and the distribution of IgA and IgG antibody-secreting cells (ASCs) in yaks. The palatine tonsils of twenty clinically healthy yaks, viz. newborn juvenile, adult and aged, were studied using histology, immunohistochemistry, and enzyme-linked immunosorbent assay (ELISA). The results showed that the palatine tonsils found in two tonsillar sinus were elongated kidney-shaped structures. Some external crypts and internal crypts were present. The palatine tonsils were partially enclosed by a connective tissue capsule and had trabeculae extending into the organ. Within these encapsulated organs, mucous glands were seen very obviously. Each crypt was highly branched and lined with stratified squamous non-keratinized epithelium. Several nonepithelial cells infiltrated between the epithelial cells, forming patches of reticular epithelium or lymphoepithelium. In newborn yaks, the lymphoid follicles were not observed. In other groups, the lymphoid follicles consisted of primary lymphoid follicles and secondary lymphoid follicles. Both IgA and IgG ASCs were distributed in the interfollicular areas, lymphoid follicles, the subepithelial areas of the nonreticular crypt epithelium, and the reticular crypt epithelium, with a few positive cells aggregated around the gland. The density of the two ASCs and the expression of the two proteins gradually increased from newborn to adult and reached a peak at adult age; they then decreased with age. However, the density of the IgG ASCs and the expression of IgG protein was significantly higher than that of IgA in all groups (P<0.01). The results indicated that the palatine tonsils were not only lymphoepithelial structures but also typical secondary lymphoid organs. IgG could be a significant component of mucosal immune responses in the palatine tonsils of yaks