Organelles harbour pH gradients.

Area of Science:

• Cell Biology
• Biochemistry
• Physiology

Background:

• Organelle pH is crucial for cellular identity and function, regulating protein modification and trafficking.
• Dysregulated organelle pH is linked to various diseases, highlighting its importance in cellular homeostasis.
• Current understanding assumes uniform pH within organelles, based on rapid proton diffusion.

Purpose of the Study:

• To investigate the spatial distribution of pH within organelles at high resolution.
• To challenge the prevailing assumption of uniform organelle pH.
• To explore the implications of pH gradients on organelle function and cellular health.

Main Methods:

• Development and application of a novel pH reporter sensitive from pH 5.5 to 10.5.
• High-resolution mapping of pH within various organelles, including the endoplasmic reticulum (ER), mitochondria, and nucleolus.
• Analysis of pH gradients in both membrane-bound and membrane-less organelles.

Main Results:

• Discovery of significant pH gradients within single organelles, such as the ER and mitochondria.
• Identification of pH gradients in membrane-less organelles like the nucleolus, independent of ion-transporting proteins.
• Evidence that organelle pH is not spatially uniform, contrary to previous assumptions.

Conclusions:

• The existence of intra-organelle pH gradients fundamentally alters our understanding of organelle physiology.
• These findings prompt new investigations into proton diffusion dynamics within cells.
• The discovery necessitates re-evaluation of pH-dependent cellular processes and their role in disease.