Paraneoplastic Cerebellar Degeneration in Nasopharyngeal Carcinoma: a Unique Association.

Paraneoplastic cerebellar degeneration (PCD) is a rare disorder that is associated with lung or gynecological malignancies and Hodgkin lymphoma. Neurologic symptoms are commonly the initial presenting sign leading to the diagnosis of an underlying malignancy. We are presenting an Asian male with progressive lower extremity weakness with EBV-positive nasopharyngeal carcinoma (NPC) and anti-Yo antibodies. Peculiarly, transient diffuse leptomeningeal enhancement is seen on MR imaging. This is the first report of PCD associated with NPC and thus illustrates that PCD embodies a boarder set of disease than previously described.

The BPS domain of Grb10 inhibits the catalytic activity of the insulin and IGF1 receptors.

Grb7, Grb10 and Grb14 comprise a family of adaptor proteins that interact with numerous receptor tyrosine kinases upon receptor activation. Between the pleckstrin homology (PH) domain and the Src homology 2 (SH2) domain of these proteins is a region of approximately 50 residues known as the BPS (between PH and SH2) domain. Here we show, using purified recombinant proteins, that the BPS domain of Grb10 directly inhibits substrate phosphorylation by the activated tyrosine kinase domains of the insulin receptor and the insulin-like growth factor 1 (IGF1) receptor. Although inhibition by the BPS domain is dependent on tyrosine phosphorylation of the kinase activation loop, peptide competition experiments indicate that the BPS domain does not bind directly to phosphotyrosine. These studies provide a molecular mechanism by which Grb10 functions as a negative regulator of insulin- and/or IGF1-mediated signaling.

Torsion-angle molecular dynamics as a new efficient tool for NMR structure calculation.

Molecular dynamics in torsion-angle space was applied to nuclear magnetic resonance structure calculation using nuclear Overhauser effect-derived distances and J-coupling-constant-derived dihedral angle restraints. Compared to two other commonly used algorithms, molecular dynamics in Cartesian space and metric-matrix geometry combined with Cartesian molecular dynamics, the method shows increased computational efficiency and success rate for large proteins, and it shows a dramatically increased radius of convergence for DNA. The torsion-angle molecular dynamics algorithm starts from an extended strand conformation and proceeds in four stages: high-temperature torsion-angle molecular dynamics, slow-cooling torsion-angle molecular dynamics, Cartesian molecular dynamics, and minimization. Tests were carried out using experimental NMR data for protein G, interleukin-8, villin 14T, and a 12 base-pair duplex of DNA, and simulated NMR data for bovine pancreatic trypsin inhibitor. For villin 14T , a monomer consisting of 126 residues, structure determination by torsion-angle molecular dynamics has a success rate of 85%, a more than twofold improvement over other methods. In the case of the 12 base-pair DNA duplex, torsion-angle molecular dynamics had a success rate of 52% while Cartesian molecular dynamics and metric-matrix distance geometry always failed.