Endoplasmain

Endoplasmain is a hypothetical cellular organelle described in speculative biology and some science fiction literature. It is proposed to form a continuous network of membranous tubules and cisternae within the cytoplasm, positioned in proximity to the endoplasmic reticulum. In these accounts, the endoplasmain is distinguished by a unique complement of membrane proteins and luminal chaperones that are not part of the classical ER.

Structure and organization: The endoplasmain is imagined as a reticular system consisting of flattened sheets and elongated tubules that interface with ER membranes through contact sites. Its lumen is suggested to harbor specialized chaperone complexes and enzymes, distinct from those found in the ER. Some depictions describe vesicular connections that shuttle cargo between the endoplasmain and ER, as part of a broader quality-control network.

Proposed functions: In speculative models, endoplasmain is thought to participate in folding and maturation of specific secretory proteins, coordinate lipid synthesis with ER processes, and modulate calcium signaling within the organelle network. It is sometimes described as a regulatory hub linking ER stress responses to cytoplasmic metabolic pathways.

Research status: There is no experimental evidence for an endoplasmain in real cells. The concept remains confined to theoretical discussions, speculative simulations, and fictional portrayals. Some researchers argue that existing organelle networks can account for observed phenomena, making the endoplasmain a controversial and largely hypothetical construct.