Lysosome membrane permeability to anions

Area of Science:

• Cell Biology
• Biochemistry
• Membrane Transport

Background:

• Lysosomes are key organelles for cellular degradation.
• Understanding lysosomal permeability is crucial for drug delivery and disease research.
• Specific transporters regulate lysosomal content, but non-specific permeation also occurs.

Purpose of the Study:

• To investigate the permeability of rat liver lysosomes to various inorganic and aliphatic organic anions.
• To determine the relationship between anion structure and lysosomal membrane permeation.
• To explore the mechanisms underlying anion transport across the lysosomal membrane.

Main Methods:

• Lysosomes were isolated from rat liver.
• An osmotic-protection methodology was employed using lysosomal hexosaminidase latency as a marker.
• Lysosomes were incubated in solutions containing potassium salts of different anions at 25°C with valinomycin.

Main Results:

• Anion permeance decreased in the order: thiocyanate, nitrate, iodide > bromide > chloride > sulfate.
• This order did not align with known anion transporters but resembled the lyotropic series.
• For organic acids, permeation correlated with the undissociated acid's pKa, suggesting a role for both undissociated and anionic forms.

Conclusions:

• Lysosomal permeability to anions is influenced by factors beyond specific transporter affinity, including charge and molecular properties.
• The lyotropic series may provide a better model for inorganic anion permeation than known transporters.
• Both undissociated organic acids and their anionic forms can permeate the lysosomal membrane.