Effects of glycosylation and pH conditions in the dynamics of human arylsulfatase A

Extremely low arylsulfatase A enzyme activity does not necessarily cause symptoms: A long-term follow-up and review of the literature

Metachromatic leukodystrophy (MLD) is an autosomal recessive lysosomal storage disease caused by deficiency of arylsulfatase A (ARSA). Heterozygous carriers of disease-causing variants and individuals harbouring pseudodeficiency alleles in the ARSA gene exhibit reduced ARSA activity. In the context of these genotypes, low ARSA activity has been suggested to lead to an atypical form of MLD or other neurological abnormalities, but data are limited. The aim of our study was to analyse the impact of low ARSA activity in two subjects who are heterozygous for the ARSA pseudodeficiency allele and a disease-causing variant. Biochemical testing included ARSA activity measurements and urinary sulfatide analysis. Biochemical data of a large cohort of MLD patients, heterozygotes, pseudodeficient individuals and healthy controls were analysed. MRI was performed at 3T using T1- and T2-weighted sequences and MR spectroscopy. We present two long-term follow-ups who are heterozygous for the ARSA pseudodeficiency allele and a disease-causing variant in the ARSA gene in cis. The two related index cases exhibit markedly reduced ARSA activity compared to controls and heterozygous carriers. The neurological evaluation and MRI do not reveal any abnormalities. Our data underline that extremely low enzyme activity due to a pseudodeficiency allele and a disease-causing variant in the ARSA gene even in cis does not lead to clinical symptoms or pre-symptomatic MRI changes suspicious for MLD. The review of literature corroborates that any association of low ARSA activity with disease features remains questionable. It seems important to combine the measurement of ARSA activity with elevated sulfatide as well as genetic testing, as done in current newborn screening approaches. Heterozygosity for metachromatic leukodystrophy and an arylsulfatase A pseudodeficiency allele does not cause neurological or neuropsychiatric features.

A model of metformin mitochondrial metabolism in metachromatic leukodystrophy: first description of human Schwann cells transfected with CRISPR-Cas9

Metachromatic leukodystrophy is a neurological lysosomal deposit disease that affects public health despite its low incidence in the population. Currently, few reports are available on pathophysiological events related to enzyme deficiencies and subsequent sulfatide accumulation. This research aims to examine the use of metformin as an alternative treatment to counteract these effects. This was evaluated in human Schwann cells (HSCs) transfected or non-transfected with CRISPR-Cas9, and later treated with sulfatides and metformin. This resulted in transfected HSCs showing a significant increase in cell reactive oxygen species (ROS) production when exposed to 100 µM sulfatides (p = 0.0007), compared to non-transfected HSCs. Sulfatides at concentrations of 10 to 100 µM affected mitochondrial bioenergetics in transfected HSCs. Moreover, these analyses showed that transfected cells showed a decrease in basal and maximal respiration rates after exposure to 100 µM sulfatide. However, maximal and normal mitochondrial respiratory capacity decreased in cells treated with both sulfatide and metformin. This study has provided valuable insights into bioenergetic and mitochondrial effects of sulfatides in HSCs for the first time. Treatment with metformin (500 µM) restored the metabolic activity of these cells and decreased ROS production.

MOWGLI: prediction of protein-MannOse interacting residues With ensemble classifiers usinG evoLutionary Information

Proteins interact with carbohydrates to perform various cellular interactions. Of the many carbohydrate ligands that proteins bind with, mannose constitute an important class, playing important roles in host defense mechanisms. Accurate identification of mannose-interacting residues (MIR) may provide important clues to decipher the underlying mechanisms of protein-mannose interactions during infections. This study proposes an approach using an ensemble of base classifiers for prediction of MIR using their evolutionary information in the form of position-specific scoring matrix. The base classifiers are random forests trained by different subsets of training data set Dset128 using 10-fold cross-validation. The optimized ensemble of base classifiers, MOWGLI, is then used to predict MIR on protein chains of the test data set Dtestset29 which showed a promising performance with 92.0% accurate prediction. An overall improvement of 26.6% in precision was observed upon comparison with the state-of-art. It is hoped that this approach, yielding enhanced predictions, could be eventually used for applications in drug design and vaccine development.

The Calcium Goes Meow: Effects of Ions and Glycosylation on Fel d 1, the Major Cat Allergen

The major cat allergen, Fel d 1, is a structurally complex protein with two N-glycosylation sites that may be filled by different glycoforms. In addition, the protein contains three putative Ca2+ binding sites. Since the impact of these Fel d 1 structure modifications on the protein dynamics, physiology and pathology are not well established, the present work employed computational biology techniques to tackle these issues. While conformational effects brought upon by glycosylation were identified, potentially involved in cavity volume regulation, our results indicate that only the central Ca2+ ion remains coordinated to Fel d 1 in biological solutions, impairing its proposed role in modulating phospholipase A2 activity. As these results increase our understanding of Fel d 1 structural biology, they may offer new support for understanding its physiological role and impact into cat-promoted allergy.

The Calcium Goes Meow: Effects of Ions and Glycosylation on Fel d 1, the Major Cat Allergen

The major cat allergen, Fel d 1, is a structurally complex protein with two N-glycosylation sites that may be filled by different glycoforms. In addition, the protein contains three putative Ca²⁺ binding sites. Since the impact of these Fel d 1 structure modifications on the protein dynamics, physiology and pathology are not well established, the present work employed computational biology techniques to tackle these issues. While conformational effects brought upon by glycosylation were identified, potentially involved in cavity volume regulation, our results indicate that only the central Ca²⁺ ion remains coordinated to Fel d 1 in biological solutions, impairing its proposed role in modulating phospholipase A₂ activity. As these results increase our understanding of Fel d 1 structural biology, they may offer new support for understanding its physiological role and impact into cat-promoted allergy.