‘Factory’ in Cells Found to Prevent Insulin Abnormalities

Jiji Press

12:34 JST, November 19, 2025

SENDAI (Jiji Press) — An international research group including Japan has discovered a factory-like system in cells that prevents insulin abnormalities, a finding that may help the development of new treatments for diabetes.

The system, which assembles insulin in its correct form and prevents abnormalities of the blood sugar-lowering substance, was found in a structure inside a cell called the endoplasmic reticulum.

The group of researchers from Tohoku University and many other Japanese universities as well as British and South Korean scientists published the finding in the British journal Nature Cell Biology on Nov. 11.

Proteins including insulin work properly in their correct forms, but in an abnormal shape they lose their functions or even cause diseases.

Previous studies have found that the endoplasmic reticulum assembles proteins correctly and prevents abnormalities in them. The detailed mechanism was unclear, however.

Tohoku University Associate Prof. Masaki Okumura and other members focused on the protein disulfide isomerase (PDI) family, a group of molecules that help the structural formation of proteins in the endoplasmic reticulum.

They examined the effects of calcium on more than 20 kinds of PDI family molecules, given that calcium concentrations are high in the endoplasmic reticulum.

The team found that one type of PDI molecule gathered and formed a compartment within the endoplasmic reticulum when calcium levels were high. This compartment assembled normal insulin and prevented structural abnormalities, according to the team.

Okumura believes that the same mechanism works for the formation of other proteins.

“Because it prevents structural abnormalities, we can expect that drugs that reduce the accumulation of defective proteins [which cause diseases such as Alzheimer’s] will be developed,” Okumura said.