Molecular dynamics simulations to decipher the structural and functional consequences of pathogenic missense mutations in the galactosylceramidase (GALC) protein causing Krabbe's disease
JOURNAL OF BIOMOLECULAR STRUCTURE & DYNAMICS
Authors: Kumar, Thirumal D.; Jain, Nikita; Kumar, Udhaya S.; Jena, Prangya Paramita; Ramamoorthy, Siva; Doss, George Priya C.; Zayed, Hatem
Abstract
Krabbe disease (KD), also known as globoid cell leukodystrophy disease, is an autosomal recessive lysosomal storage genetic disorder, which is caused by the deficiency of galactocerebrosidase (GALC) coding gene (GALC). This study aimed to use extensive computational pipelines in understanding the missense mutations in GALC. We retrieved 176 mutations from the public databases and subjected them to pathogenicity, stability, and conservation analyses. The PredictSNP, iStable, and ConSurf prediction tools predicted 45, 95, and 47 mutations to be deleterious, destabilizing, and highly conserved, respectively. The R396L and R396W were the most deleterious and destabilizing to GALC, and were therefore prioritized for further analysis. Systematic validation on the impact of the R396L and R396W mutations to the chaperone alpha lobeline was performed using the molecular docking approach. The docking analysis revealed that the mutant R396W interacted with minimal binding affinity compared with both the R396L mutant and native GALC. Furthermore, the repetitive molecular dynamics simulation analysis showed that the mutant R396W demonstrated less compactness and reduced number of intramolecular hydrogen bonds compared with the mutant R396L and the native GALC. Overall, we observed higher structural and functional modifications in R396W positioned in the substrate-binding site. This was highly supported by the MMPBSA and DSSP analysis of the GROMACS. DSSP showed the transformation of turns to bends, indicating a loss of stability due to the R396W mutation. This study is expected to serve as a platform for prioritizing mutant proteins that could be a platform for both drug and target therapeutics Communicated by Ramaswamy H. Sarma
Cell mimetic monolayer supported chitosan-haemocompatibility studies
JOURNAL OF BIOMEDICAL MATERIALS RESEARCH PART A
Authors: Mathews, Smitha; Kaladhar, K.; Sharma, Chandra P.
Abstract
Chitosan is a natural polymer, widely explored for biomedical and tissue engineering applications. However the thrombogenic nature limits their application in blood contacting devices and implants. Here, we have attempted to understand the haemocompatibility of chitosan by immobilizing a monolayer of cell mimetic lipid compositions. The phosphatidylcholine/cholesterol/galactocerebroside lipid composition (PC/Chol/GalC, 1:0.35:0.125) was deposited onto the chitosan films. Characterization of the modified surface was done by sessile drop contact angle measurement. The contact angle of the chitosan film reduced from 80.65 +/- 1.4 to 23.5 +/- 1.9 after the surface modification. Swelling nature of chitosan seemed to influence the orientation and packing of the lipid monolayer. In vitro calcification studies with metastable salt solution indicated increased calcification on the modified surface. This may be due to formation of nuclei for calcification on the expanding monolayer. The preliminary haemocompatibility studies with washed platelets, leukocytes and erythrocytes showed overall reduction in blood cell adhesion to the modified surfaces. Scanning electron microscopy was used for morphological characterization of platelet adhesion and activation on the surfaces. On the bare chitosan surface, fully spread platelets with extending pseudopodia indicated platelet activation. The smooth surface of the modified film did not activate platelets. These studies showed that, though the lipid monolayer on chitosan film is able to reduce the over all blood cell adhesion and platelet activation it is prone to calcification. (c) 2006 Wiley Periodicals, Inc.