small molecules
2023-07-07 | Identification of Regulatory Molecular “Hot Spots” for LH/PLOD Collagen Glycosyltransferase Activity
Hydroxylysine glycosylations are post-translational modifications (PTMs) essential for the maturation and homeostasis of fibrillar and non-fibrillar collagen molecules. The multifunctional collagen lysyl hydroxylase 3 (LH3/PLOD3) and the collagen galactosyltransferase GLT25D1 are the human enzymes that have been identified as being responsible for the glycosylation of collagen lysines, although a precise description of the contribution of each enzyme to these essential PTMs has not yet been provided in the literature. LH3/PLOD3 is thought to be capable of performing two chemically distinct collagen glycosyltransferase reactions using the same catalytic site: an inverting beta-1,O-galactosylation of hydroxylysines (Gal-T) and a retaining alpha-1,2-glucosylation of galactosyl hydroxylysines (Glc-T). In this work, we have combined indirect luminescence-based assays with direct mass spectrometry-based assays and molecular structure studies to demonstrate that LH3/PLOD3 only has Glc-T activity and that GLT25D1 only has Gal-T activity. Structure-guided mutagenesis confirmed that the Glc-T activity is defined by key residues in the first-shell environment of the glycosyltransferase catalytic site as well as by long-range contributions from residues within the same glycosyltransferase (GT) domain. By solving the molecular structures and characterizing the interactions and solving the molecular structures of human LH3/PLOD3 in complex with different UDP-sugar analogs, we show how these studies could provide insights for LH3/PLOD3 glycosyltransferase inhibitor development. Collectively, our data provide new tools for the direct investigation of collagen hydroxylysine PTMs and a comprehensive overview of the complex network of shapes, charges, and interactions that enable LH3/PLOD3 glycosyltransferase activities, expanding the molecular framework and facilitating an improved understanding and manipulation of glycosyltransferase functions in biomedical applications.
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1996-11-01 | Prophylactic laser photocoagulation in stickler syndrome
The ocular manifestations in a family with Stickler syndrome and the results of laser photocoagulation as preventive treatment for retinal detachment are described. Forty-two family members with Stickler syndrome were retrospectively reviewed; 22 had ocular abnormalities, 22 had myopia and 16 had high myopia. Ten patients had developed retinal detachment and 9 of them were blind in one or both eyes because of irreparable detachment. Only 2 eyes had been operated on successfully. Ten eyes were lasered prophylactically. In eyes with extensive vitreoretinopathy laser burns were applied 360° around the peripheral retina at the border between the pathological and normal retina. Eyes with isolated lesions received focal treatment around the pathological areas. Four eyes received 360° laser photocoagulation and 6 eyes received focal treatment. Of the treated cases, 9 retinas remained attached for a follow-up period ranging from 1 to 15 years. One patient was lost to follow-up, and 5 years later developed retinal detachment in one eye from a new non-lasered lesion. In conclusion, in this particular family the incidence of retinal detachment was significantly higher in non-lasered eyes than in lasered eyes (p<0.025).
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