The identification of pathways necessary for photoreceptor and retinal pigment epithelium (RPE) function is critical to uncover blindness therapies. Here we report the discovery of adiponectin receptor 1 (AdipoR1) as a regulator of these cells’ functions. Docosahexaenoic acid (DHA) is avidly retained in photoreceptors, while mechanisms controlling DHA uptake and retention are unknown. Thus, we demonstrate that AdipoR1 ablation results in DHA reduction. In situ hybridization reveals photoreceptor and RPE cell AdipoR1 expression, blunted in AdipoR1−/− mice. We also find decreased photoreceptor-specific phosphatiydylcholine containing very long chain polyunsaturated fatty acids and severely-attenuated electroretinograms. These changes precede progressive photoreceptor degeneration in AdipoR1−/− mice. RPE-rich eyecup cultures from AdipoR1−/− reveal impaired DHA uptake. AdipoR1 overexpression in RPE cells enhances DHA uptake, whereas AdipoR1 silencing has the opposite effect. These results establish AdipoR1 as a regulatory switch of DHA uptake, retention, conservation, and elongation in photoreceptors and RPE, thus preserving photoreceptor cell integrity.
Inhibition of vascular endothelial growth factor, a key contributor to the choroidal neovascularization associated with wet age-related macular degeneration, is the mode of action of several approved therapies, including aflibercept, which requires frequent intravitreal injections to provide clinical benefit. Lack of compliance with the dosing schedule may result in recurrence of active wet macular degeneration, leading to irreversible vision impairment. Gene therapy providing sustained anti-vascular endothelial growth factor levels in the retina following a single injection could drastically reduce the treatment burden and improve visual outcomes. ADVM-022, an adeno-associated virus vector encoding aflibercept, is optimized for intravitreal delivery and strong protein expression. Here, we report the long-term expression and efficacy of ADVM-022-derived aflibercept in a laser-induced choroidal neovascularization model in non-human primates. Intravitreal administration of ADVM-022 was well tolerated and resulted in sustained aflibercept levels. In addition, ADVM-022 administration 13 months before lasering prevented the occurrence of clinically relevant choroidal neovascularization lesions, similar to animals that received a bolus of intravitreal aflibercept (standard of care) at the time of lesioning. These results demonstrate that a single intravitreal administration of ADVM-022 may provide a safe and effective long-term treatment option for wet macular degeneration and may ultimately improve patients’ visual outcomes.
Mice deficient in GNPTAB exhibited severe retinal degeneration. Additional features observed in patients with ML II, a lysosomal storage disease, are also present in these mice. Understanding underlying mechanisms of this gene in the eye will increase its therapeutic potential for the treatment of retinal diseases.
UDP-GlcNAc:lysosomal enzyme N-acetylglucosamine-1-phosphotransferase (GlcNAc-1-phosphotransferase) mediates the first step in the synthesis of the mannose 6-phosphate recognition marker on acid hydrolases. The transferase exists as an ␣ 2  2 ␥ 2 hexameric complex with the ␣-and -subunits derived from a single precursor molecule. The catalytic function of the transferase is attributed to the ␣-and -subunits, whereas the ␥-subunit is believed to be involved in the recognition of a conformation-dependent protein determinant common to acid hydrolases. Using knock-out mice with mutations in either the ␣/ gene or the ␥ gene, we show that disruption of the ␣/ gene completely abolishes phosphorylation of high mannose oligosaccharides on acid hydrolases whereas knock-out of the ␥ gene results in only a partial loss of phosphorylation. These findings demonstrate that the ␣/-subunits, in addition to their catalytic function, have some ability to recognize acid hydrolases as specific substrates. This process is enhanced by the ␥-subunit.
Abstract. UDP-GlcNAc: lysosomal enzyme N-acetylglucosamine-1-phosphotransferase (GlcNAc-1-phosphotransferase) is an a 2 b 2 c 2 hexameric enzyme that catalyzes the first step in the synthesis of the mannose 6-phosphate targeting signal on lysosomal hydrolases. In humans, mutations in the gene encoding the a/b subunit precursor give rise to mucolipidosis II (MLII), whereas mutations in the gene encoding the c subunit cause the less severe mucolipidosis IIIC (MLIIIC). In this study we describe the phenotypic, histologic, and serum lysosomal enzyme abnormalities in knockout mice lacking the c subunit and compare these findings to those of mice lacking the a/b subunits and humans with MLII and MLIIIC. We found that both lines of mutant mice had elevated levels of serum lysosomal enzymes and cytoplasmic alterations in secretory cells of several exocrine glands; however, lesions in c-subunit deficient (Gnptg 2/2 ) mice were milder and more restricted in distribution than in a/b-subunit deficient (Gnptab 2/2 ) mice. We found that onset, extent, and severity of lesions that developed in these two different knockouts correlated with measured lysosomal enzyme activity; with a more rapid, widespread, and severe storage disease phenotype developing in Gnptab 2/2 mice. In contrast to mice deficient in the a/b subunits, the mice lacking the c subunits were of normal size, lacked cartilage defects, and did not develop retinal degeneration. The milder disease in the c-subunit deficient mice correlated with residual synthesis of the mannose 6-phosphate recognition marker. Of significance, neither strain of mutant mice developed cytoplasmic vacuolar inclusions in fibrocytes or mesenchymal cells (I-cells), the characteristic lesion associated with the prominent skeletal and connective tissue abnormalities in humans with MLII and MLIII. Instead, the predominant lesions in both lines of mice were found in the secretory epithelial cells of several exocrine glands, including the pancreas, and the parotid, submandibular salivary, nasal, lacrimal, bulbourethral, and gastric glands. The absence of retinal and chondrocyte lesions in Gnptg 2/2 mice might be attributed to residual b-glucuronidase activity. We conclude that mice lacking either a/b or c subunits displayed clinical and pathologic features that differed substantially from those reported in humans having mutations in orthologous genes.
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