medialGolgi

The medial Golgi is a functional region of the Golgi apparatus in eukaryotic cells, situated between the cis-Golgi network receiving cargo from the endoplasmic reticulum and the trans-Golgi network that sorts proteins for delivery. It is part of the stacked cisternae that constitute the Golgi and participates in modifying cargo as it traverses the secretory pathway.

Within the Golgi stack, the medial cisternae host specific enzymes responsible for processing nascent glycoproteins and lipids. Notable medial-Golgi enzymes include mannosidase II and N-acetylglucosaminyltransferases I and II, which refine N-linked oligosaccharides as part of the maturation toward complex-type and hybrid glycans. The medial compartment also contributes to certain O-linked glycan processing steps and other carbohydrate modifications.

Functionally, the medial Golgi participates in maturation and quality control of secreted and membrane proteins by trimming and building glycans, which can influence protein folding, stability, trafficking, and interactions. The exact distribution of enzymes can vary among organisms and cell types, but the medial stage is generally defined by its enzymatic repertoire and location in the stack.

Disruption or mutations affecting medial-Golgi enzymes can alter glycosylation patterns and are associated with congenital disorders of glycosylation and related diseases. The medial Golgi therefore plays a key role in post-translational modification, sorting, and trafficking of cellular cargo.