p38 MAPK activation and STIM1-Orai3 association mediate TRPC6 externalization

Area of Science:

• Vascular Biology
• Cell Signaling
• Ion Channels

Background:

• Endothelial cell (EC) migration is vital for vascular repair after angioplasty.
• Lipid oxidation products, such as lysophosphatidylcholine (lysoPC), impair EC migration by activating TRPC6 channels.
• The source of calcium influx and the precise mechanism of TRPC6 channel activation by lysoPC remain unclear.

Purpose of the Study:

• To elucidate the signaling pathway by which lysoPC activates TRPC6 channels and inhibits EC migration.
• To identify key molecular players involved in lysoPC-induced EC dysfunction.
• To explore potential therapeutic strategies to preserve EC migration.

Main Methods:

• Investigated the role of arachidonic acid (ArA) and its metabolites in lysoPC-induced calcium signaling.
• Utilized p38 MAPK and Src kinase inhibitors to block specific signaling nodes.
• Employed small interfering RNA (siRNA) to downregulate Orai3 expression.
• Measured intracellular calcium ([Ca2+]i) levels and TRPC6 channel externalization.
• Assessed endothelial cell migration in response to lysoPC treatment under various conditions.

Main Results:

• LysoPC activates phospholipase A2, releasing ArA, which in turn activates arachidonic acid-regulated calcium (ARC) channels (STIM1-Orai3/1).
• Both lysoPC and ArA activate p38 MAPK, leading to STIM1-Orai3 association and increased [Ca2+]i.
• Elevated [Ca2+]i activates Src kinase, promoting TRPC6 channel externalization and inhibiting EC migration.
• Downregulation of Orai3 using siRNA abrogated lysoPC-induced [Ca2+]i increase and TRPC6 externalization, preserving EC migration.

Conclusions:

• LysoPC-induced inhibition of EC migration is mediated by a pathway involving p38 MAPK, STIM1-Orai3 complex, and subsequent Src kinase activation leading to TRPC6 channel externalization.
• Targeting Orai3 or p38 MAPK can counteract the detrimental effects of lipid oxidation products on endothelial function.
• This study reveals a novel mechanism for TRPC6 channel regulation and offers a potential therapeutic avenue for preventing post-angioplasty restenosis.