PKD2/polycystin-2 induces autophagy by forming a complex with BECN1

Area of Science:

• Cell Biology
• Molecular Biology
• Autophagy Research

Background:

• Macroautophagy/autophagy is a fundamental cellular process for degrading macromolecules and organelles.
• Polycystin 2 (PKD2/PC2/TRPP2), a cation channel, is known to be essential for autophagy, but the underlying mechanism is unclear.
• Understanding the molecular players and interactions governing autophagy is crucial for cellular health and disease research.

Purpose of the Study:

• To elucidate the molecular mechanism by which PKD2 regulates autophagy.
• To identify the specific interaction between PKD2 and key autophagy proteins.
• To determine the role of calcium (Ca²⁺) and PKD2's structural domains in autophagy regulation.

Main Methods:

• Investigated the physical and functional interaction between PKD2 and beclin 1 (BECN1) using co-immunoprecipitation and functional assays.
• Utilized BAPTA-AM to deplete intracellular Ca²⁺ and assess its impact on autophagy and the PKD2-BECN1 complex.
• Employed overexpression of wild-type PKD2 and a Ca²⁺ channel-deficient mutant (PKD2^D509V) to study their effects on autophagy induction and BECN1 interaction.

Main Results:

• PKD2 forms a direct physical and functional complex with BECN1, a crucial protein for autophagosome formation.
• This interaction is mediated by the coiled-coil domain (CCD) of PKD2 (specifically CC1) and depends on intracellular Ca²⁺ levels.
• PKD2 overexpression enhances autophagy and BECN1 interaction, while a non-functional PKD2 mutant fails to induce autophagy or interact with BECN1.

Conclusions:

• The formation of the PKD2-BECN1 complex is essential for the induction of autophagy.
• Intracellular Ca²⁺ mobilization by PKD2 and the integrity of its CC1 domain are critical for this interaction and subsequent autophagy.
• These findings reveal a novel mechanism for PKD2-mediated autophagy regulation, highlighting the importance of the PKD2-BECN1 complex and calcium signaling.