Yop1p information

This article is an orphan, as no other articles link to it. Please introduce links to this page from related articles; try the Find link tool for suggestions. (September 2017)

DP1/Yop1p is an integral membrane protein family that, along with the reticulons, is responsible for the shape of the tubular endoplasmic reticulum (ER) in yeast and mammalian cells. Furthermore, it is also believed that they might be involved in sheet ER formation.^[1]

About half the total area of membrane in an eukaryotic cell encloses the space of the endoplasmic reticulum. The ER is an extremely dynamic membrane organelle which consists of the nuclear envelope and the peripheral ER. It is organized into a netlike labyrinth of branching tubules and flattened sheets that extends throughout the cytosol. These tubules and sheets are interconnected and their membrane is continuous with the outer nuclear membrane. The ER and nuclear membranes form a continuous layer enclosing a single internal space, called the ER lumen, which often occupies the 10% of the total cell volume.^[2] However, this unique space has several morphologically distinct areas.^[3] Thus, the peripheral ER is composed of a polygonal network of tubules and interdispersed sheets that spreads from the nuclear envelope to the cell cortex.

At an ultrastructural level, the ER can be classified into two types, rough ER (RER) and smooth ER (SER). The RER has a sheet-like morphology and its main feature is the presence of ribosomes. Conversely, the SER is devoid of ribosomes and tends to be more tubular in structure.

The peripheral ER is dynamic: the tubules continuously form and disappear and the sheets rearrange.^[4] ER shaping proteins (reticulons and Dp1/Yop1p) play key roles in generating and maintaining this unique reticular morphology of the ER. An intact peripheral ER is functionally important in higher eukaryotes. Failure to maintain this structure could be related to certain neurological disorders.

In all eukaryotic cells, the ER plays an important role in decisive processes, such as the biosynthesis of secretory and membrane proteins, protein modification, lipid synthesis and calcium storage (used in many cell signaling responses).

Both mammalian DP1 (for "deleted in polyposis") and Yop1p in yeast cells are ubiquitously expressed and found in most eukaryotic cells. They are predominantly localized to the tubular ER and to the highly curved edges of ER sheets.