Researchers in Ottawa and collaborators in the United States say they have uncovered a protein that functions like a molecular pillar inside mitochondria, physically spacing the organelle’s two membranes and thereby controlling a tiny but crucial compartment known as the intermembrane space (IMS).
How a spacer shapes mitochondrial function
Mitochondria generate the bulk of a cell’s chemical energy and rely on a compact internal layout: an outer membrane and an inner membrane separated by the IMS. The new study, published in Science Advances, identifies a protein the authors call SPRIZ — an acronym for SPatial Regulator of the mitochondrial Intermembrane Zone — that physically links the two membranes while holding them a set distance apart.
“What makes SPRIZ so unexpected is that it uses a familiar mechanism—a tether—to do something different: it connects the two mitochondrial membranes while acting as a rigid pillar that holds them a set distance apart, so the room between them keeps a defined height,” explains Dr. Luca Pellegrini, full professor at the University of Ottawa, who led the study.
That defined height of the IMS matters because the narrow space helps sustain the chemical gradients and reactions required for ATP production. By altering where the IMS widens or narrows within a mitochondrion, cells can reshape the organelle’s internal geometry and, in turn, adjust its functional output.
Methods that tied structure to genetics
The research combined computational modelling, genetic experiments, broad protein surveys and high-resolution imaging. Among the imaging tools was three-dimensional electron tomography, which allowed the team to visualise mitochondrial architecture in fine detail and to see SPRIZ spanning the two membranes.
The authors say the convergence of these approaches was key: molecular simulations predicted plausible tethering behaviours; genetics linked the protein to structural outcomes; and proteomics and tomography provided the physical evidence of a pillar-like connection.
Why this matters for disease and cell biology
SPRIZ’s ability to actively set the IMS volume opens a new line of inquiry into why mitochondria fail in disease and how damaged organelles are recognised and cleared. The paper points to possible relevance in conditions where mitochondria underperform or are inadequately removed, citing Parkinson’s disease as one example where disrupted mitochondrial maintenance is implicated.
The finding reframes a long-held assumption that mitochondrial spacing is merely passive or incidental. Instead, spacing becomes a genetically regulated parameter that cells can tune — adding a layer of control over bioenergetics and quality control that was not previously appreciated.
- SPRIZ acts as a rigid bridge between inner and outer mitochondrial membranes.
- The protein sets and maintains the height of the intermembrane space, an element important to energy production chemistry.
- The study used computer simulation, genetics, protein analysis and 3D electron tomography to show structure and function are linked.
| Feature | Implication |
|---|---|
| Structural role of SPRIZ | Maintains fixed spacing between membranes |
| Adjustable IMS volume | Allows cells to tune mitochondrial function |
| Technique suite | Combined modelling, genetics, proteomics, 3D tomography |
Although the team highlights potential disease links, the paper does not claim immediate clinical applications. Instead, it sets a foundation for follow-up studies to determine whether altering SPRIZ or IMS spacing can modify mitochondrial performance in living tissues and whether that could be targeted to correct dysfunction.
For cell biologists, the discovery also raises mechanistic questions: how is SPRIZ regulated, how widespread is its presence across cell types and species, and how does IMS spacing interact with other processes such as mitochondrial fission, fusion and mitophagy? Answers to those questions could reframe aspects of mitochondrial biology and metabolism.
The study demonstrates how a single structural protein can exert outsized influence on organelle architecture and highlights the continuing importance of integrating computational and imaging approaches to unlock cellular mechanisms.
As research groups pursue the next steps, the notion that cells actively govern the internal dimensions of their powerhouses adds a new chapter to our understanding of cellular energy management and its failures in disease.
