Endoplasmakalvoston

Endoplasmakalvoston is a membranous organelle within many eukaryotic cells that forms an interconnected network of flattened sacs and tubular filaments distributed throughout the cytoplasm. In most cells, it is physically connected to the nuclear envelope and extends into the cytosol, creating a continuous lumen that communicates with the perinuclear space.

Molecular organization: It consists of rough endoplasmakalvoston, studded with ribosomes on its cytosolic surface, and smooth endoplasmakalvoston, which lacks ribosomes. The rough portion is specialized for protein synthesis and folding, while the smooth portion is enriched in enzymes for lipid metabolism and detoxification. The lumen of both domains is continuous.

Functions: Synthesis and processing of secretory, membrane, and lysosomal proteins; glycosylation and folding assisted by chaperones; insertion of proteins into the membrane; synthesis of phospholipids and cholesterol; sequestration and release of calcium ions; detoxification of certain metabolites in liver and other tissues.

Trafficking and interactions: Proteins produced in the rough domain are packaged into transport vesicles that bud from the endoplasmakalvoston and move to the Golgi apparatus and other destinations. The organelle forms contact sites with mitochondria, lysosomes, and peroxisomes and participates in lipid exchange and signaling. Its structure can be remodeled by cytoskeletal elements and ER-shaping proteins as cells change activity.

Clinical and research relevance: Dysfunctions of the endoplasmakalvoston are linked to accumulation of misfolded proteins, triggering the unfolded protein response and potentially leading to cellular stress and disease. Understanding its function is important in cell biology, physiology, and biotechnology. The term endoplasmakalvoston is used in some language variants as an equivalent term for the endoplasmic reticulum.