Related Experiment Video
Updated: Mar 2, 2026
A Mass Spectrometry-Based Approach to Identify Phosphoprotein Phosphatases and their Interactors
Published on: April 29, 2022
A Single Kinase Generates the Majority of the Secreted Phosphoproteome
Vincent S Tagliabracci1, Sandra E Wiley1, Xiao Guo2
1Department of Pharmacology, University of California, San Diego, La Jolla, CA 92093, USA.
Abstract:
The existence of extracellular phosphoproteins has been acknowledged for over a century. However, research in this area has been undeveloped largely because the kinases that phosphorylate secreted proteins have escaped identification. Fam20C is a kinase that phosphorylates S-x-E/pS motifs on proteins in milk and in the extracellular matrix of bones and teeth. Here, we show that Fam20C generates the majority of the extracellular phosphoproteome. Using CRISPR/Cas9 genome editing, mass spectrometry, and biochemistry, we identify more than 100 secreted phosphoproteins as genuine Fam20C substrates. Further, we show that Fam20C exhibits broader substrate specificity than previously appreciated. Functional annotations of Fam20C substrates suggest roles for the kinase beyond biomineralization, including lipid homeostasis, wound healing, and cell migration and adhesion. Our results establish Fam20C as the major secretory pathway protein kinase and serve as a foundation for new areas of investigation into the role of secreted protein phosphorylation in human biology and disease.
Insights
Fam20C is identified as the major kinase responsible for most extracellular protein phosphorylation. This discovery opens new avenues for understanding secreted protein roles in various biological processes and diseases.
Area of Science:
- Biochemistry
- Molecular Biology
- Cell Biology
Background:
- Extracellular phosphoproteins have been known for over a century, but their study was limited by the lack of identified kinases.
- Identifying these kinases is crucial for understanding secreted protein function and regulation.
Purpose of the Study:
- To identify the major kinase responsible for extracellular protein phosphorylation.
- To characterize the substrates and functions of this kinase.
Main Methods:
- CRISPR/Cas9 genome editing
- Mass spectrometry
- Biochemical assays
Main Results:
- Fam20C was identified as the kinase responsible for the majority of the extracellular phosphoproteome.
- Over 100 secreted phosphoproteins were confirmed as Fam20C substrates.
- Fam20C demonstrated broader substrate specificity than previously known, with roles beyond biomineralization.
Conclusions:
- Fam20C is established as the predominant secretory pathway protein kinase.
- Fam20C substrates are involved in lipid homeostasis, wound healing, cell migration, and adhesion.
- This work provides a foundation for investigating secreted protein phosphorylation in human health and disease.
Related Concept Videos
01:22Amplifying Signals via Enzymatic Cascade
02:54Protein Kinases and Phosphatases
Protein kinases
Many proteins in the cell are regulated by phosphorylation, the addition of a phosphate group. A family of enzymes called kinases...
02:54Protein Kinases and Phosphatases
01:22PI3K/mTOR/AKT Signaling Pathway
01:02Phosphorylation
During phosphorylation, protein kinases transfer the terminal phosphate group of ATP to specific amino acid side chains of substrate proteins. Serine, threonine, and tyrosine are the most commonly...
01:15Amplifying Signals via Second Messengers