Browsing by Author "Lewandowski, Dominik"

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    MFRP is a molecular hub that organizes the apical membrane of RPE cells by engaging in interactions with specific proteins and lipids
    (National Academy of Sciences, 2025) Tworak, Aleksander; Smidak, Roman; Rodrigues Menezes, Carolline; Du, Samuel W.; Suh, Susie; Choi, Elliot H.; Imanishi, Sanae S.; Dong, Zhiqian; Lewandowski, Dominik; Fong, Kristen E.; Grigorean, Gabriela; Pinto, Antonio F. M.; Xu, Qianlan; Skowronska-Krawczyk, Dorota; Blackshaw, Seth; Imanishi, Yoshikazu; Palczewski, Krzysztof; Ophthalmology, School of Medicine
    Membrane frizzled-related protein (MFRP), present in the retinal pigment epithelium (RPE), is an integral membrane protein essential for ocular development and the normal physiology of the retina. Mutations in MFRP are associated with autosomal recessive nonsyndromic nanophthalmos, leading to severe hyperopia and early-onset retinitis pigmentosa. While several preclinical gene-augmentation and gene-editing trials hold promise for future therapies aimed at stopping degeneration and restoring retinal function, the molecular mechanisms involved in MFRP biology are still not well understood. Here, we studied the biochemical properties of MFRP and the molecular consequences of its loss of function in the retinal degeneration 6 (rd6) mouse model. Using transcriptomic and lipidomic approaches, we observed that accumulation of docosahexaenoic acid (DHA) constitutes a primary defect in the MFRP-deficient RPE. In biochemical assays, we showed that MFRP undergoes extensive glycosylation, and it preferentially binds lipids of several classes, including phosphatidylserine and phosphatidylinositol-4-phosphate; as well as binding to several transmembrane proteins, notably adiponectin receptor 1 (ADIPOR1) and inward rectifier potassium channel 13 (KCNJ13). Moreover, MFRP determines the subcellular localization of ADIPOR1 and KCNJ13 in the RPE in vivo. This feature is altered by MFRP deficiency and can be restored by gene-therapy approaches. Overall, our observations suggest that MFRP constitutes an important interaction hub within the apical membrane of RPE cells, coordinating protein trafficking and subcellular localization within the RPE, and lipid homeostasis within the entire retina.
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    Restoring retinal polyunsaturated fatty acid balance and retina function by targeting ceramide in AdipoR1-deficient mice
    (Elsevier, 2024) Lewandowski, Dominik; Gao, Fangyuan; Imanishi, Sanae; Tworak, Aleksander; Bassetto, Marco; Dong, Zhiqian; Pinto, Antonio F. M.; Tabaka, Marcin; Kiser, Philip D.; Imanishi, Yoshikazu; Skowronska-Krawczyk, Dorota; Palczewski, Krzysztof; Ophthalmology, School of Medicine
    Mutations in the adiponectin receptor 1 gene (AdipoR1) lead to retinitis pigmentosa and are associated with age-related macular degeneration. This study explores the effects of AdipoR1 gene deficiency in mice, revealing a striking decline in ω3 polyunsaturated fatty acids (PUFA), an increase in ω6 fatty acids, and elevated ceramides in the retina. The AdipoR1 deficiency impairs peroxisome proliferator-activated receptor α signaling, which is crucial for FA metabolism, particularly affecting proteins associated with FA transport and oxidation in the retina and retinal pigmented epithelium. Our lipidomic and proteomic analyses indicate changes that could affect membrane composition and viscosity through altered ω3 PUFA transport and synthesis, suggesting a potential influence of AdipoR1 on these properties. Furthermore, we noted a reduction in the Bardet-Biedl syndrome proteins, which are crucial for forming and maintaining photoreceptor outer segments that are PUFA-enriched ciliary structures. Diminution in Bardet-Biedl syndrome-proteins content combined with our electron microscopic observations raises the possibility that AdipoR1 deficiency might impair ciliary function. Treatment with inhibitors of ceramide synthesis led to substantial elevation of ω3 LC-PUFAs, alleviating photoreceptor degeneration and improving retinal function. These results serve as the proof of concept for a ceramide-targeted strategy to treat retinopathies linked to PUFA deficiency, including age-related macular degeneration.