ST8SIA1

ST8SIA1 is a human gene that encodes polysialyltransferase 1, an enzyme responsible for forming polysialic acid chains on glycoproteins, most notably the neural cell adhesion molecule (NCAM). The encoded protein is a type II transmembrane enzyme located in the Golgi apparatus and belongs to the glycosyltransferase family 29. It catalyzes the addition of sialic acid residues in alpha-2,8 linkages to create extended polysialic acid chains on target glycoproteins.

Polysialylation by ST8SIA1 modulates cell surface interactions. The presence of polysialic acid on NCAM reduces cell–cell adhesion and promotes processes such as neuronal migration, axon elongation, and synaptic remodeling during development. PSA-NCAM is particularly abundant in the developing nervous system and is generally reduced as neural maturation progresses, though it may be re-expressed during plasticity or in certain disease states.

Expression of ST8SIA1 is highest in developing brain tissue, with lower levels in other tissues. Its activity can influence neural connectivity and plasticity, and alterations in polysialylation patterns have been studied in the context of neural development disorders and oncogenesis. In some cancers and neural tumors, increased PSA-NCAM expression has been observed and is a subject of research as a potential biomarker or therapeutic target.

ST8SIA1 is part of a small family of polysialyltransferases, with related members such as ST8SIA2 and ST8SIA4 also contributing to polysialylation in different tissues and developmental contexts.