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Congenital disorders of glycosylation. Part II. Defects of protein O-glycosylation

100%

Cylwik B., Lipartowska K., Chrostek L., Gruszewska E.

2013

vol. 60

issue 3

361-368

Glycosylation is a form of post-translational modification of proteins and occurs in every living cell. The carbohydrate chains attached to the proteins serve various functions. There are two main types of protein glycosylation: N-glycosylation and O-glycosylation. In this paper, we describe the O-glycosylation process and currently known congenital disorders of glycosylation associated with defects of protein O-glycosylation. This process takes place in the cis Golgi apparatus after N-glycosylation and folding of the proteins. The O-glycosylation is essential in the biosynthesis of mucins, the formation of proteoglycan core proteins and blood group proteins. Most common forms of O-glycans are the mucin-type glycans. There are more than 20 known disorders related to O-glycosylation disturbances. We review 8 of the following diseases linked to defects in the synthesis of O-xylosylglycans, O-N acetylgalactosaminylglycans, O-xylosyl/N-acetylglycans, O-mannosylglycans, and O-fucosylglycans: multiple exostoses, progeroid variant of Ehlers-Danlos syndrome, progeria, familial tumoral calcinosis, Schneckenbecken dysplasia, Walker-Warburg syndrome, spondylocostal dysostosis type 3, and Peter's plus syndrome. Causes of these diseases include gene mutations and deficiency of proteins (enzymes). Their diagnosis includes syndromic presentation, organ-specific expression and laboratory findings.

Congenital disorders of glycosylation. Part I. Defects of protein N-glycosylation

100%

Cylwik B., Naklicki M., Chrostek L., Gruszewska E.

2013

vol. 60

issue 2

151-161

Glycosylation is the most common chemical process of protein modification and occurs in every living cell. Disturbances of this process may be either congenital or acquired. Congenital disorders of glycosylation (CDG) are a rapidly growing disease family, with about 50 disorders reported since its first clinical description in 1980. Most of the human diseases have been discovered recently. CDG result from defects in the synthesis of the N- and O-glycans moiety of glycoproteins, and in the attachment to the polypeptide chain of proteins. These defects have been found in the activation, presentation, and transport of sugar precursors, in the enzymes responsible for glycosylation, and in proteins that control the traffic of component. There are two main types of protein glycosylation: N-glycosylation and O-glycosylation. Most diseases are due to defects in the N-glycosylation pathway. For the sake of convenience, CDG were divided into 2 types, type I and II. CDG can affect nearly all organs and systems. The considerable variability of clinical features makes it difficult to recognize patients with CDG. Diagnosis can be made on the basis of abnormal glycosylation display. In this paper, an overview of CDG with a new nomenclature limited to the group of protein N-glycosylation disorders, clinical phenotype and diagnostic approach, have been presented. The location, reasons for defects, and the number of cases have been also described. This publication aims to draw attention to the possibility of occurrence of CDG in each multisystem disorder with an unknown origin.

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2 Acta Biochimica Polonica

2 2013

2 Chrostek L.

2 Cylwik B.

2 Gruszewska E.

1 Lipartowska K.

1 Naklicki M.

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Congenital disorders of glycosylation. Part II. Defects of protein O-glycosylation

Congenital disorders of glycosylation. Part I. Defects of protein N-glycosylation