Migalastat improves diarrhea in patients with Fabry disease: clinical-biomarker correlations from the phase 3 FACETS trial

Background: Fabry disease is frequently characterized by gastrointestinal symptoms, including diarrhea. Migalastat is an orally-administered small molecule approved to treat the symptoms of Fabry disease in patients with amenable mutations. Methods: We evaluated minimal clinically important differences (MCID) in diarrhea based on the corresponding domain of the patient-reported Gastrointestinal Symptom Rating Scale (GSRS) in patients with Fabry disease and amenable mutations (N = 50) treated with migalastat 150 mg every other day or placebo during the phase 3 FACETS trial (NCT00925301). Results: After 6 months, significantly more patients receiving migalastat versus placebo experienced improvement in diarrhea based on a MCID of 0.33 (43% vs 11%; p = .02), including the subset with baseline diarrhea (71% vs 20%; p = .02). A decline in kidney peritubular capillary globotriaosylceramide inclusions correlated with diarrhea improvement; patients with a reduction > 0.1 were 5.6 times more likely to have an improvement in diarrhea than those without (p = .031). Conclusions: Migalastat was associated with a clinically meaningful improvement in diarrhea in patients with Fabry disease and amenable mutations. Reductions in kidney globotriaosylceramide may be a useful surrogate endpoint to predict clinical benefit with migalastat in patients with Fabry disease. Trial registration NCT00925301; June 19, 2009

Stability and membrane orientation of the fukutin transmembrane domain: a combined multiscale molecular dynamics and circular dichroism study

The N-terminal domain of Fukutin-I has been implicated in the localization of the protein in the endoplasmic reticulum/Golgi apparatus. It has been proposed to mediate this through its interaction with the thinner lipid bilayers found in these compartments. Here we have employed multi-scale molecular dynamics simulations and circular dichroism spectroscopy to explore the structure, stability and orientation of the short 36-residue N-terminal of Fukutin-I (FK1TMD) in lipids of differing tail lengths. Our results show that FK1TMD adopts a stable helical conformation in phosphatidylcholine lipids when orientated with its principal axis perpendicular to the bilayer plane. The stability of the helix is largely insensitive to the lipid tail length, avoiding hydrophobic mismatch by virtue of its mobility and ability to tilt within the lipid bilayers. This suggests that changes in FK1TMD tilt in response to bilayer properties may be implicated in the regulation of its trafficking. Coarse-grained simulations of the complex Golgi membrane suggest the N-terminal domain may induce the formation of microdomains in the surrounding membrane through its preferential interaction with 1,2-dipalmitoyl-sn-glycero-3-phoshpatidylinositol 4,5-bisphosphate (PIP2) lipids

Electroporation of the E. coli and S. Aureus membranes: molecular dynamics simulations of complex bacterial membranes

Bacterial membranes are complex organelles composed of a variety of lipid types. The differences in their composition are a key factor in determining their relative permeabilities. The success of antibacterial agents depends upon their interaction with bacterial membranes, yet little is known about the molecular-level interactions within membranes of different bacterial species. To address this, we have performed molecular dynamics simulations of two bacterial membranes: the outer membrane of E. coli and the cell membrane of S. aureus . We have retained the chemical complexity of the membranes by considering the details of their lipidic components. We identify the extended network of lipid-lipid interactions that stabilize the membranes. Our simulations of electroporation show that the S. aureus cell membrane is less resistant to poration than the E. coli outer membrane. The mechanisms of poration for the two membranes have subtle differences; for the E. coli outer membrane, relative differences in mobilities of the lipids of both leaflets are key in the process of poratio

The NorM MATE transporter from N. gonorrhoeae: insights into drug and ion Binding from atomistic molecular dynamics simulations

The multidrug and toxic compound extrusion transporters extrude a wide variety of substrates out of both mammalian and bacterial cells via the electrochemical gradient of protons and cations across the membrane. The substrates transported by these proteins include toxic metabolites and antimicrobial drugs. These proteins contribute to multidrug resistance in both mammalian and bacterial cells and are therefore extremely important from a biomedical perspective. Although specific residues of the protein are known to be responsible for the extrusion of solutes, mechanistic details and indeed structures of all the conformational states remain elusive. Here, we report the first, to our knowledge, simulation study of the recently resolved x-ray structure of the multidrug and toxic compound extrusion transporter, NorM from Neisseria gonorrhoeae (NorM_NG). Multiple, atomistic simulations of the unbound and bound forms of NorM in a phospholipid lipid bilayer allow us to identify the nature of the drug-protein/ion-protein interactions, and secondly determine how these interactions contribute to the conformational rearrangements of the protein. In particular, we identify the molecular rearrangements that occur to enable the Na+ ion to enter the cation-binding cavity even in the presence of a bound drug molecule. These include side chain flipping of a key residue, GLU-261 from pointing toward the central cavity to pointing toward the cation binding side when bound to a Na+ ion. Our simulations also provide support for cation binding in the drug-bound and apo states of NorM_NG