Complementary charge-driven encapsulation of functional protein by engineered protein cages in cellulo

Area of Science:

• Biochemistry
• Molecular Biology
• Cell Biology

Background:

• Protein cages are supramolecular structures with potential applications in drug delivery and biomaterials.
• Understanding the principles of host-guest complexation within these cages is crucial for their effective utilization.
• Live-cell environments present unique challenges for the stability and function of encapsulated molecules.

Purpose of the Study:

• To investigate the mechanisms of charge-driven inclusion complex formation within protein cages in live cells.
• To determine the key factors governing the stability and protective capacity of protein cages for guest molecules.
• To assess the role of host-guest ionic interactions and cage integrity in cellular encapsulation.

Main Methods:

• Utilized a degradation-prone fluorescent protein as a model guest molecule.
• Employed a series of engineered protein cages with varying properties.
• Performed live-cell imaging and fluorescence microscopy to monitor complex formation and protein degradation.
• Analyzed the impact of ionic strength and protein cage structure on guest encapsulation efficiency.

Main Results:

• Demonstrated that charge-driven interactions are a primary driver for inclusion complex formation in live cells.
• Showcased that protein cage integrity, specifically an intact shell-like structure, is critical for preventing guest degradation.
• Found that sufficiently strong host-guest ionic interactions enhance the stability and protective encapsulation of the guest protein.
• Observed that incomplete or damaged cages lead to rapid guest protein denaturation and loss of function.

Conclusions:

• Charge-driven host-guest interactions are vital for forming stable inclusion complexes within protein cages in a cellular context.
• The structural integrity of the protein cage shell is paramount for providing a protective environment for encapsulated guests.
• These findings highlight the importance of optimizing both ionic interactions and cage architecture for successful in vivo applications of protein cage systems.