Endoplasmin

Endoplasmin (HSP90B1) is an ATP-dependent chaperone localized to the endoplasmic reticulum that facilitates protein processing, folding, and transport (UniProt: P14625). The protein regulates canonical Wnt signaling by promoting LRP6 folding in conjunction with MESD, and collaborates with CNPY3 to ensure proper folding and trafficking of Toll-like receptors to the cell surface. It may also mediate translocation of leaderless cytosolic cargo, such as interleukin-1, into the ERGIC for secretion via the TMED10 cargo receptor.

Endoplasmin functions broadly in endoplasmic reticulum quality control and secretory pathway regulation, with roles spanning immune receptor maturation and developmental signaling cascades. No specific disease associations are annotated in UniProt.

In Alzheimer's Disease, endoplasmin shows ambiguous regulation across subcellular fractions in post-mortem AD brain tissue compared to age-matched controls, based on quantitative proteomics analysis (Chaparral AD proteomics). The mean log2 fold-change was 0.404 across three examined fractions in a four-fraction TMT-labeled mass spectrometry experiment, indicating inconsistent directional change depending on subcellular localization. This pattern suggests compartment-specific alterations in endoplasmic reticulum chaperone function in AD pathology.