Effect of receptor occupancy on folate receptor internalization

Area of Science:

• Cell Biology
• Pharmacology
• Oncology

Background:

• The folate receptor (FR) is a cell surface glycoprotein crucial for folic acid uptake and signal transduction.
• Targeted therapies utilizing FR are increasingly used in clinical settings.
• Understanding FR dynamics is vital for optimizing drug dosing and efficacy.

Purpose of the Study:

• To investigate the impact of folate receptor (FR) occupancy on its internalization rate.
• To determine if FR occupancy influences the availability of FR for subsequent drug uptake.
• To compare the internalization rates of monovalent and multivalent FR-binding molecules.

Main Methods:

• Quantification of cell surface FR-α and FR-β after exposure to saturating concentrations of folate-linked molecules and anti-FR antibodies.
• Utilized unmodified folate, folate-linked drug mimetics, multifolate nanoparticles, and monoclonal antibodies.
• Compared internalization rates of monovalent and multivalent FR conjugates.

Main Results:

• Folate receptor occupancy was found to have no impact on the rate of FR internalization.
• Multivalent conjugates that cross-link FRs internalized at the same rate as monovalent folate conjugates.
• Despite similar internalization rates, multivalent conjugates utilized a different endocytic pathway than monovalent conjugates.

Conclusions:

• Cell surface folate receptor internalization rate is independent of receptor occupancy.
• Dosing frequency of FR-targeted drugs may not be limited by FR availability due to internalization rates.
• Multivalent FR-binding molecules and monovalent folate conjugates share similar internalization kinetics despite distinct cellular trafficking.