Selective export of autotaxin from the endoplasmic reticulum

Area of Science:

• Molecular Biology
• Cell Biology
• Biochemistry

Background:

• Autotaxin (ATX), also known as ectonucleotide pyrophosphatase/phosphodiesterase 2 (ENPP2), is a crucial secretory enzyme in generating lysophosphatidic acid.
• The precise mechanisms governing ATX protein trafficking and secretion remain largely unelucidated.

Purpose of the Study:

• To identify the protein-sorting receptors and molecular machinery involved in the endoplasmic reticulum (ER) export of ATX.
• To investigate the role of signaling pathways in regulating ATX secretion.

Main Methods:

• Utilized p23 knockdown and siRNA-mediated knockdown of Sec24 isoforms to assess their role in ATX trafficking.
• Identified a di-phenylalanine motif in ATX essential for p23 interaction.
• Investigated the influence of AKT signaling on p23 expression and ATX secretion.

Main Results:

• p23 was identified as the essential protein-sorting receptor for ER export of ATX.
• A di-phenylalanine motif (Phe-838/Phe-839) in ATX mediates its interaction with p23.
• ER export of ATX was specifically impaired upon Sec24C downregulation.
• AKT signaling positively regulates ATX secretion by enhancing nuclear factor of activated T cell-mediated p23 expression.
• The identified ER export mechanism is conserved in other ENPP family members (ENPP1 and ENPP3) possessing similar C-terminal di-hydrophobic motifs.

Conclusions:

• ATX is selectively exported from the ER via a pathway involving p23 and Sec24C.
• AKT signaling modulates ATX secretion through p23 expression.
• This p23, Sec24C-dependent ER export mechanism is conserved across the ENPP family, suggesting a common regulatory principle for these enzymes.