“…These results indicate that D409V has greater unfavorable energy environment than D409H that could result in their differential in vivo hydrolytic properties. D409 is within the GCase binding motif ( 399 DSPIIVDITKD 409 ) for LIMP-2 (lysosomal integral membrane protein 2), the internal trafficking chaperone of GCase for lysosomal targeting 28,29 . Mutation at this position (D409V, D409H) leads to an unstable enzymes that predisposed them to protease degradation compared to WT.Figure 1Modeling of mutation effect on GCase structure.…”
Section: Resultsmentioning
confidence: 99%
“…Domain 1 (residues1–27 and 383–414), where D409 resides, is predicted to be important in enzyme folding and stability, domain 2 (residues 30–75 and 431–497) has an immunoglobulin-like structure, and domain 3 (residues 76–381 and 416–430) forms TIM barrel-helix6 and helix7 consisting of catalytic site 13,30 . LIMP2 is an intracellular receptor for lysosomal targeting of GCase 28,32 . The binding motif of GCase for LIMP2 is contained in the span covered by amino acids 399 to 409 in Domain III of GCase 28,29 .…”
Section: Discussionmentioning
confidence: 99%
“…LIMP2 is an intracellular receptor for lysosomal targeting of GCase 28,32 . The binding motif of GCase for LIMP2 is contained in the span covered by amino acids 399 to 409 in Domain III of GCase 28,29 . The mutant GCases, D409V or H, disrupts lysosomal targeting of these GCases leading to their proteolysis.…”
Gaucher disease is caused by mutations in
GBA1
encoding acid β-glucosidase (GCase). Saposin C enhances GCase activity and protects GCase from intracellular proteolysis. Structure simulations indicated that the mutant GCases, N370S (0 S), V394L (4L) and D409V(9V)/H(9H), had altered function. To investigate the
in vivo
function of
Gba1
mutants, mouse models were generated by backcrossing the above homozygous mutant GCase mice into Saposin C deficient (C*) mice. Without saposin C, the mutant GCase activities in the resultant mouse tissues were reduced by ~50% compared with those in the presence of Saposin C. In contrast to 9H and 4L mice that have normal histology and life span, the 9H;C* and 4L;C* mice had shorter life spans. 9H;C* mice developed significant visceral glucosylceramide (GC) and glucosylsphingosine (GS) accumulation (GC»GS) and storage macrophages, but lesser GC in the brain, compared to 4L;C* mice that presents with a severe neuronopathic phenotype and accumulated GC and GS primarily in the brain. Unlike 9V mice that developed normally for over a year, 9V;C* pups had a lethal skin defect as did 0S;C* mice resembled that of 0S mice. These variant Gaucher disease mouse models presented a mutation specific phenotype and underscored the
in vivo
role of Saposin C in the modulation of Gaucher disease.
“…These results indicate that D409V has greater unfavorable energy environment than D409H that could result in their differential in vivo hydrolytic properties. D409 is within the GCase binding motif ( 399 DSPIIVDITKD 409 ) for LIMP-2 (lysosomal integral membrane protein 2), the internal trafficking chaperone of GCase for lysosomal targeting 28,29 . Mutation at this position (D409V, D409H) leads to an unstable enzymes that predisposed them to protease degradation compared to WT.Figure 1Modeling of mutation effect on GCase structure.…”
Section: Resultsmentioning
confidence: 99%
“…Domain 1 (residues1–27 and 383–414), where D409 resides, is predicted to be important in enzyme folding and stability, domain 2 (residues 30–75 and 431–497) has an immunoglobulin-like structure, and domain 3 (residues 76–381 and 416–430) forms TIM barrel-helix6 and helix7 consisting of catalytic site 13,30 . LIMP2 is an intracellular receptor for lysosomal targeting of GCase 28,32 . The binding motif of GCase for LIMP2 is contained in the span covered by amino acids 399 to 409 in Domain III of GCase 28,29 .…”
Section: Discussionmentioning
confidence: 99%
“…LIMP2 is an intracellular receptor for lysosomal targeting of GCase 28,32 . The binding motif of GCase for LIMP2 is contained in the span covered by amino acids 399 to 409 in Domain III of GCase 28,29 . The mutant GCases, D409V or H, disrupts lysosomal targeting of these GCases leading to their proteolysis.…”
Gaucher disease is caused by mutations in
GBA1
encoding acid β-glucosidase (GCase). Saposin C enhances GCase activity and protects GCase from intracellular proteolysis. Structure simulations indicated that the mutant GCases, N370S (0 S), V394L (4L) and D409V(9V)/H(9H), had altered function. To investigate the
in vivo
function of
Gba1
mutants, mouse models were generated by backcrossing the above homozygous mutant GCase mice into Saposin C deficient (C*) mice. Without saposin C, the mutant GCase activities in the resultant mouse tissues were reduced by ~50% compared with those in the presence of Saposin C. In contrast to 9H and 4L mice that have normal histology and life span, the 9H;C* and 4L;C* mice had shorter life spans. 9H;C* mice developed significant visceral glucosylceramide (GC) and glucosylsphingosine (GS) accumulation (GC»GS) and storage macrophages, but lesser GC in the brain, compared to 4L;C* mice that presents with a severe neuronopathic phenotype and accumulated GC and GS primarily in the brain. Unlike 9V mice that developed normally for over a year, 9V;C* pups had a lethal skin defect as did 0S;C* mice resembled that of 0S mice. These variant Gaucher disease mouse models presented a mutation specific phenotype and underscored the
in vivo
role of Saposin C in the modulation of Gaucher disease.
“…). Interestingly, Limp2 has been reported to bind cholesterol and phosphatidylcholine in structural studies . In the context of lysosomal, neurodegenerative disorders, Limp2 has been proposed as a marker of Gaucher and Parkinson disease .…”
Niemann–Pick disease, type C1 (NPC1) is a fatal, autosomal recessive, neurodegenerative disorder caused by mutations in the NPC1 gene. As a result, there is accumulation of unesterified cholesterol and sphingolipids in the late endosomal/lysosomal system. This abnormal accumulation results in a cascade of pathophysiological events including progressive, cerebellar neurodegeneration, among others. While significant progress has been made to better understand NPC1, the downstream effects of cholesterol storage and the major mechanisms that drive neurodegeneration remain unclear. In the current study, a) the use of a commercial, highly efficient standard flow‐ESI platform for protein biomarker identification is implemented and b) protein biomarkers are identified and evaluated at a terminal time point in the NPC1 null mouse model. In this study, alterations are observed in proteins related to fatty acid homeostasis, calcium binding and regulation, lysosomal regulation, and inositol biosynthesis and metabolism, as well as signaling by Rho family GTPases. New observations from this study include altered expression of Pcp2 and Limp2 in Npc1 mutant mice relative to control, with Pcp2 exhibiting multiple isoforms and specific to the cerebella. This study provides valuable insight into pathways altered in the late‐stage pathophysiology of NPC1.
“…[ 33 ] While bounding with beta-glucocerebrosidase (GBA), LIMP2 can transfer GBA from the endoplasmic reticulum to the lysosome. [ 34 35 36 37 38 39 ] SCARB2 protein comprises two TM domains and one CD36-like domain, which contains a highly conserved coiled-coil domain (residue: 145-288 aa) that binds GBA [ Figure 4 ]. [ 35 36 37 ] Mutations in the SCARB2 gene result in decreasing and anomaly location of SCARB2 protein, affecting the combination of SCARB and GBA.…”
Background:Progressive myoclonus epilepsies (PMEs) comprise a group of rare genetic disorders characterized by action myoclonus, epileptic seizures, and ataxia with progressive neurologic decline. Due to clinical and genetic heterogeneity of PMEs, it is difficult to decide which genes are affected. The aim of this study was to report an action myoclonus with or without renal failure syndrome (EPM4) family and summarize the clinical and genetic characteristics of all reported EPM4 patients.Methods:In the present study, targeted next-generation sequencing (NGS) was applied to screen causative genes in a Chinese PME family. The candidate variant was further confirmed by cosegregation analysis and further functional analysis, including the reverse transcription polymerase chain reaction and Western blot of the proband's muscle. Moreover, literature data on the clinical and mutational features of all reported EPM4 patients were reviewed.Results:The gene analysis revealed a novel homozygous splicing mutation (c.995-1G>A) of the SCARB2 gene in two brothers. Further functional analysis revealed that this mutation led to loss function of the SCARB2 protein. The classification of the candidate variant, according to the American College of Medical Genetics and Genomics standards and guidelines and functional analysis, was pathogenic. Therefore, these two brothers were finally diagnostically confirmed as EPM4.Conclusions:These present results suggest the potential for targeted NGS to conduct a more rapid and precise diagnosis for PME patients. A literature review revealed that mutations in the different functional domains of SCARB2 appear to be associated with the phenotype of EPM4.
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