Exploring the Multiligand Binding Specificity of Saposin B Reveals Two Binding Sites

Tinklepaugh, Jay; Smith, Britannia M.; Hanlon, Etta; Zubieta, Chloé; Bou-Abdallah, Fadi; Doyle, Robert P.

doi:10.1021/acsomega.7b01334

Cited by 5 publications

(3 citation statements)

References 24 publications

(65 reference statements)

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“…Our simulations indicate that an open SapB dimer binds at least two Gb3-NBD molecules. Furthermore, these results are consistent with reports describing in vitro experiments showing SapB dimers binding two phospholipids 50 and in silico experiments showing SapB dimers binding two small molecules 51 .…”

Section: Discussionsupporting

confidence: 92%

Human Saposin B Ligand Binding and Presentation to α-Galactosidase A

Sawyer,

Aral,

Staros

et al. 2024

Preprint

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Sphingolipid activator protein B (saposin B; SapB) is an essential activator of globotriaosylceramide (Gb3) catabolism by α-galactosidase A. However, the manner by which SapB stimulates α-galactosidase A activity remains unknown. To uncover the molecular mechanism of SapB presenting Gb3 to α-galactosidase A, we subjected the fluorescent substrate globotriaosylceramide-nitrobenzoxidazole (Gb3-NBD) to a series of biochemical and structural assays involving SapB. First, we showed that SapB stably binds Gb3-NBD using a fluorescence equilibrium binding assay, isolates Gb3-NBD from micelles, and facilitates α-galactosidase A cleavage of Gb3-NBD in vitro. Second, we crystallized SapB in the presence of Gb3-NBD and validated the ligand-bound assembly. Third, we captured transient interactions between SapB and α-galactosidase A by chemical cross-linking. Finally, we determined the crystal structure of SapB bound to α-galactosidase A. These findings establish general principles for molecular recognition in saposin:hydrolase complexes and highlight the utility of NBD reporter lipids in saposin biochemistry and structural biology.

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Section: Discussionsupporting

confidence: 92%

Human Saposin B Ligand Binding and Presentation to α-Galactosidase A

Sawyer,

Aral,

Staros

et al. 2024

Preprint

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“…To our knowledge, no specific small-molecule inhibitor has been developed for this purpose. However, from literature, we found that the antimalarial drug hydroxychloroquine binds to saposin B (47). Hydroxychloroquine is an immunomodulating drug used to treat rheumatoid arthritis and systemic lupus erythematosus (SLE), and recent studies showed antiatherosclerotic effects in patients with SLE (48,49).…”

Section: Discussionmentioning

confidence: 99%

Prosaposin mediates inflammation in atherosclerosis

et al. 2021

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Macrophages play a central role in the pathogenesis of atherosclerosis. The inflammatory properties of these cells are dictated by their metabolism, of which the mechanistic target of rapamycin (mTOR) signaling pathway is a key regulator. Using myeloid cell–specific nanobiologics in apolipoprotein E–deficient (Apoe−/−) mice, we found that targeting the mTOR and ribosomal protein S6 kinase-1 (S6K1) signaling pathways rapidly diminished plaque macrophages’ inflammatory activity. By investigating transcriptome modifications, we identified Psap, a gene encoding the lysosomal protein prosaposin, as closely related with mTOR signaling. Subsequent in vitro experiments revealed that Psap inhibition suppressed both glycolysis and oxidative phosphorylation. Transplantation of Psap−/− bone marrow to low-density lipoprotein receptor knockout (Ldlr−/−) mice led to a reduction in atherosclerosis development and plaque inflammation. Last, we confirmed the relationship between PSAP expression and inflammation in human carotid atherosclerotic plaques. Our findings provide mechanistic insights into the development of atherosclerosis and identify prosaposin as a potential therapeutic target.

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“…Their results suggest that the binding of one molecule of CoQ 10 may accelerate the binding of two molecules of α-tocopherol. The crystal structure of saposin B binding chloroquine was later resolved [153] and molecular docking studies identified two binding sites that are accessible to a variety of ligands [154].…”

Section: Saposin B Binds Coq 10 and Regulates Coq 10 Contentmentioning

confidence: 99%

New Insights on the Uptake and Trafficking of Coenzyme Q

Guile,

Jain,

Anderson

et al. 2023

Antioxidants

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Coenzyme Q (CoQ) is an essential lipid with many cellular functions, such as electron transport for cellular respiration, antioxidant protection, redox homeostasis, and ferroptosis suppression. Deficiencies in CoQ due to aging, genetic disease, or medication can be ameliorated by high-dose supplementation. As such, an understanding of the uptake and transport of CoQ may inform methods of clinical use and identify how to better treat deficiency. Here, we review what is known about the cellular uptake and intracellular distribution of CoQ from yeast, mammalian cell culture, and rodent models, as well as its absorption at the organism level. We discuss the use of these model organisms to probe the mechanisms of uptake and distribution. The literature indicates that CoQ uptake and distribution are multifaceted processes likely to have redundancies in its transport, utilizing the endomembrane system and newly identified proteins that function as lipid transporters. Impairment of the trafficking of either endogenous or exogenous CoQ exerts profound effects on metabolism and stress response. This review also highlights significant gaps in our knowledge of how CoQ is distributed within the cell and suggests future directions of research to better understand this process.

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Exploring the Multiligand Binding Specificity of Saposin B Reveals Two Binding Sites

Cited by 5 publications

References 24 publications

Human Saposin B Ligand Binding and Presentation to α-Galactosidase A

Human Saposin B Ligand Binding and Presentation to α-Galactosidase A

Prosaposin mediates inflammation in atherosclerosis

New Insights on the Uptake and Trafficking of Coenzyme Q

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