Tjap1/Pilt Is a cis-Golgi-Associated Protein Required for Golgi Integrity and Normal Drug Transporter Expression in...

Area of Science:

• Cell Biology
• Neuroscience
• Biochemistry

Background:

• Brain microvascular endothelial cells (BMECs) form the blood-brain barrier (BBB), controlling substance entry into the central nervous system.
• The role of Tight junction-associated protein 1 (Tjap1) in BMECs, particularly its localization and function, remained uncharacterized.
• Tjap1 is known to localize to tight junctions in epithelial cells and the trans-Golgi network in fibroblasts.

Purpose of the Study:

• To investigate the expression, subcellular localization, and functional significance of Tjap1 in BMECs.
• To determine the impact of Tjap1 knockout on Golgi morphology and the expression of BBB-associated transporters and receptors.

Main Methods:

• Immunofluorescence microscopy was used to determine Tjap1 localization in mouse and human BMEC cell lines and primary cells.
• CRISPR/Cas9 was employed to generate Tjap1 knockout BMECs for Golgi morphology analysis.
• Quantitative real-time PCR and Western blot assessed the expression of BBB transporters and receptors in Tjap1 knockout cells.

Main Results:

• Tjap1 was found to localize predominantly to the cis-Golgi compartment in BMECs, not tight junctions.
• Tjap1 knockout resulted in significant Golgi fragmentation in BMECs.
• Knockout of Tjap1 led to altered mRNA and protein expression of key BBB drug transporters and receptors, including downregulation of Abcb1, Abcc4, Slc2a1, Slc7a1, and Tfrc, and upregulation of Abcg2.

Conclusions:

• Tjap1 is a cis-Golgi-associated protein essential for maintaining Golgi apparatus structural integrity in BMECs.
• Tjap1 deficiency causes Golgi fragmentation and dysregulates the expression of BBB transporters and receptors.
• Tjap1 emerges as a potential regulator of BBB transporter profiles, with implications for drug transport modulation across the BBB.