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Updated: Apr 29, 2026
Real Time Monitoring of Intracellular Bile Acid Dynamics Using a Genetically Encoded FRET-based Bile Acid Sensor
Published on: January 4, 2016
Determination of Site-Specific Phosphorylation Occupancy Using Targeted Mass Spectrometry Reveals the Regulation of
Thao T Nguyen1, Maureen A Kane1, Peter W Swaan1
1Department of Pharmaceutical Sciences, University of Maryland School of Pharmacy, Baltimore, Maryland 21201, United States.
None:
The human apical bile acid transporter (hASBT, SLC10A2) reabsorbs bile acids in the distal ileum, facilitating their recycling to the liver and resecretion. Its activity has been implicated in various disease states, including Crohn's disease, hypercholesterolemia, cholestasis, and type-2 diabetes. Post-translational modifications such as N-glycosylation, ubiquitination, and S-acylation regulate ASBT function by controlling its translocation and stability. However, the precise role of phosphorylation and its relationship with activity remains unknown. Here, we employed parallel reaction monitoring targeted mass spectrometry to investigate ASBT phosphorylation in the presence of various kinase inhibitors and activators. Our study ascertains phosphorylation at multiple sites (Thr330, Ser334, and Ser335), with Ser335 being the predominant phosphosite. We further demonstrate the critical involvement of PKC in regulating ASBT activity by phosphorylation at Ser335. Importantly, we establish a proportional relationship between the phosphorylation level of Ser335 and ASBT bile acid uptake activity. Collectively, our findings shed light on the molecular mechanisms underlying phosphorylation-mediated regulation of ASBT.
