Analysis of Staphylococcus aureus proteins secreted inside infected human epithelial cells

Area of Science:

• Microbiology
• Infectious Diseases
• Proteomics

Background:

• Staphylococcus aureus is an opportunistic pathogen that invades and survives within host cells.
• Secreted virulence factors are crucial for S. aureus attachment and intracellular survival.
• Detecting these secreted factors within host cells is challenging for traditional proteomics.

Purpose of the Study:

• To identify Staphylococcus aureus HG001 proteins secreted into host cell compartments after internalization.
• To discover potential therapeutic targets by monitoring virulence factors produced during intracellular infection.
• To overcome limitations of previous proteomic approaches in detecting low-abundance secreted proteins.

Main Methods:

• Density gradient centrifugation and mass spectrometry were employed to isolate and identify secreted bacterial proteins.
• Shotgun mass spectrometry was initially used, followed by highly sensitive single reaction monitoring mass spectrometry.
• Bacterial proteins within infected human bronchial epithelial cells were quantified at 2.5 and 6.5 hours post-infection.

Main Results:

• 37 bacterial proteins were quantified within the host cell compartment.
• Identified proteins included secreted virulence factors such as lipases, pore-forming toxins, and adhesins.
• S. aureus proteome adaptation included enhanced responses to oxidative and cell wall stress.
• Increased production of adhesins and pore-forming toxins was observed, facilitating host cell attachment and lysis.

Conclusions:

• This study successfully identified low-abundance secreted virulence factors of S. aureus within host cells.
• The findings highlight the bacterium's adaptation to intracellular environments and its mechanisms for host cell manipulation.
• The identified virulence factors represent promising targets for novel anti-S. aureus therapies.