Calcium Signaling & ER Protein Quality Control

TOKYO, November 11, 2025 — A cellular quality control system, crucial for preventing diseases like Type 2 diabetes, Alzheimer’s, and ALS, operates through a surprising mechanism involving calcium and protein “droplets,” researchers have discovered.

How Cellular Droplets Could Prevent Diabetes and Neurodegenerative Diseases

New research illuminates the role of calcium in maintaining protein health within cells, offering potential avenues for treating debilitating conditions.

• Calcium ions (Ca²⁺) orchestrate protein quality control within the endoplasmic reticulum (ER).
• A process called calcium-driven phase separation creates liquid-like droplets that correct misfolded proteins.
• Misfolded proinsulin, a precursor to insulin, is linked to an increased risk of Type 2 diabetes.
• The findings, published in Nature Cell Biology, could inform drug development for currently incurable diseases.

For years, scientists have understood that calcium (Ca²⁺) is a key player in many cellular processes, but its precise role in maintaining protein quality—a process called proteostasis—remained largely a mystery. Now, an international team of researchers, led by Distinguished Associate Professor Masaki Okumura of Tohoku University in Japan, has shed light on this critical function.

Q: How do cells ensure proteins are properly folded and functional?
A: Cells utilize a process called proteostasis, which involves calcium-driven phase separation to create liquid-like droplets that correct misfolded proteins, preventing the buildup of harmful aggregates.

Calcium’s Role in Protein Folding

The team’s work, a collaborative effort involving 17 research groups from Japan, Korea, and the UK, revealed that calcium can trigger a phase separation in PDIA6, a gene responsible for protein folding within the ER. When PDIA6 doesn’t function correctly, proteins can misfold, leading to a cascade of health problems.

However, the story doesn’t end with errors. Researchers found that calcium-driven phase separation creates condensation-like droplets that act as tiny repair shops, correcting misfolded proinsulin—the precursor to insulin. Too much proinsulin can signal an increased risk for Type 2 diabetes.

“To keep everything running smoothly, we need these condensation-like droplets to ensure proinsulin is properly folded – as opposed to forming large, aggregate clumps that can disrupt the normal pathways and cause negative health outcomes,” explained Okumura.

This discovery isn’t just about diabetes. Understanding how calcium regulates proteostasis could have far-reaching implications for treating other diseases where protein misfolding plays a central role, including Alzheimer’s and amyotrophic lateral sclerosis (ALS). The research, published on November 11, 2025, in Nature Cell Biology, provides a crucial step forward in unraveling the complexities of cellular health.

This knowledge meaningfully contributes to our understanding of other calcium-driven processes within cells. Further research is needed to explore how these findings can be translated into effective therapies.