1H NMR studies of drugs with achiral and chiral lanthanide shift reagents: Applications to the anticonvulsant pheneturide

The anticonvulsant pheneturide, PNT, has been studied by 300 MHz ¹H NMR in CDCl₃ at ambient temperatures with the achiral lanthanide shift reagent (LSR) Eu(FOD)₃, and with the chiral LSR, Eu(HFC)₃. Both LSRs produced spectral simplification of the aryl proton signal region, and substantial lanthanide‐induced shifts (LIS). With added Eu(HFC)₃, enantiomeric shift differences (ΔΔδ) were induced for most nuclei of PNT, indicating substantial potential for direct determination of enantiomeric excess. Valley heights between corresponding signals in the PNT enantiomers as low as 3.6% were achieved for the meta resonance. Least squares line‐fitting was applied to the variation of chemical shift vs. [LSR]/[PNT] molar ratios for both LSRs. Tentative assignments were made for the NH absorptions based on two‐dimensional NMR (COSY45), as well as their relative magnitudes of LIS, ΔΔδ, and lanthanide‐induced line broadening. The PNT conformation reported in the crystal is believed to be retained in solution with added LSR. The relative senses of magnetic nonequivalence were found to be the same among the three sets of aryl protons, and among the three kinds of protons in the ethyl moiety, with high levels of added chiral LSR, using 2D NMR. Chirality 11:529–535, 1999. © 1999 Wiley‐Liss, Inc.     

Actin restricts FcepsilonRI diffusion and facilitates antigen-induced receptor immobilization

The actin cytoskeleton has been implicated in restricting diffusion of plasma membrane components. Here, simultaneous observations of quantum dot-labelled FcepsilonRI motion and GFP-tagged actin dynamics provide direct evidence that actin filament bundles define micron-sized domains that confine mobile receptors. Dynamic reorganization of actin structures occurs over seconds, making the location and dimensions of actin-defined domains time-dependent. Multiple FcepsilonRI often maintain extended close proximity without detectable correlated motion, suggesting that they are co-confined within membrane domains. FcepsilonRI signalling is activated by crosslinking with multivalent antigen. We show that receptors become immobilized within seconds of crosslinking. Disruption of the actin cytoskeleton results in delayed immobilization kinetics and increased diffusion of crosslinked clusters. These results implicate actin in membrane partitioning that not only restricts diffusion of membrane proteins, but also dynamically influences their long-range mobility, sequestration and response to ligand binding.     

1-Aminoindanes as novel motif with potential atypical antipsychotic properties

As part of an on-going effort to investigate the chemical space requirements for D(2)/5-HT(2A) receptor antagonists as atypical antipsychotics, new 1-aminoindanes were synthesized. The replacement of the heterocycle (oxindole) in ziprasidone with a carbocycle (indane) was well tolerated and was found to retain binding affinities for dopamine D(2), serotonin 5-HT(2A), and serotonin 5-HT(1A). Such compounds hold promise as a new chemical motif with atypical antipsychotic properties for the treatment of schizophrenia and related disorders.     

Transfer of the first arabinofuranose residue to galactan is essential for Mycobacterium smegmatis viability

The mycobacterial arabinan is an elaborate component of the cell wall with multiple glycosyl linkages and no repeating units. In Mycobacterium spp., the Emb proteins (EmbA, EmbB, and EmbC) have been identified as putative mycobacterial arabinosyltransferases implicated in the biogenesis of the cell wall arabinan. Furthermore, it is now evident that the EmbA and EmbB proteins are involved in the assembly of the nonreducing terminal motif of arabinogalactan and EmbC is involved in transferring arabinose, perhaps in the early stage of arabinan synthesis in lipoarabinomannan. It has also been shown that the Emb proteins are a target of the antimycobacterial drug ethambutol (EMB). In the search for additional mycobacterial arabinosyltransferases in addition to the Emb proteins, we disrupted MSMEG_6386 (an orthologue of Rv3792 and a gene upstream of embC) in Mycobacterium smegmatis. Allelic exchange at the chromosomal MSMEG_6386 locus of M. smegmatis could only be achieved in the presence of a rescue plasmid carrying a functional copy of MSMEG_6386 or Rv3792, strongly suggesting that MSMEG_6386 is essential. An in vitro arabinosyltransferase assay using a membrane preparation from M. smegmatis expressing Rv3792 and synthetic beta-d-Galf-(1-->5)-beta-D-Galf-(1-->6)-beta-D-Galf-octyl and beta-D-Galf-(1-->6)-beta-D-Galf-(1-->5)-beta-D-Galf-octyl showed that Rv3792 gene product can transfer an arabinose residue to the C-5 position of the internal 6-linked galactose. The reactions were insensitive to EMB, and when alpha-d-Manp-(1-->6)-alpha-D-Manp-(1-->6)-alpha-D-Manp-octylthiomethyl was used as an acceptor, no product was formed. These observations indicate that transfer of the first arabinofuranose residue to galactan is essential for M. smegmatis viability.     

Both actin and polyproline interactions of profilin-1 are required for migration, invasion and capillary morphogenesis of vascular endothelial cells

The objective of the present study was to evaluate how different ligand interactions of profilin-1 (Pfn1), an actin-binding protein that is upregulated during capillary morphogenesis of vascular endothelial cells (VEC), contribute to migration and capillary forming ability of VEC. We adopted a knockdown-knockin experimental system to stably express either fully functional form or mutants of Pfn1 that are impaired in binding to two of its major ligands, actin (H119E mutant) and proteins containing polyproline domains (H133S mutant), in a human dermal microvascular cell line (HmVEC) against near-null endogenous Pfn1 background. We found that silencing endogenous Pfn1 expression in HmVEC leads to slower random migration, reduced velocity of membrane protrusion and a significant impairment in matrigel-induced cord formation. Only re-expression of fully functional but not any of the two ligand-binding deficient mutants of Pfn1 rescues the above defects. We further show that loss of Pfn1 expression in VEC inhibits three-dimensional capillary morphogenesis, MMP2 secretion and ECM invasion. VEC invasion through ECM is also inhibited when actin and polyproline interactions of Pfn1 are disrupted. Together, these experimental data demonstrate that Pfn1 regulates VEC migration, invasion and capillary morphogenesis through its interaction with both actin and proline-rich ligands.