SLC29A1/ENT1 and SLC29A3/ENT3 differentially regulate autophagy.

Area of Science:

• Cell Biology
• Molecular Biology
• Physiology

Background:

• Equilibrative nucleoside transporters (ENTs) are crucial for nucleoside salvage, but their diverse roles beyond DNA synthesis remain explored.
• Multiple ENT subfamilies suggest specialized, non-redundant functions in maintaining cellular homeostasis.
• The interplay between ENTs and cellular processes like autophagy is not fully elucidated.

Purpose of the Study:

• To investigate the distinct roles of SLC29A1/ENT1 and SLC29A3/ENT3 in regulating autophagy.
• To elucidate the molecular mechanisms by which these transporters influence autophagic flux.
• To explore the reciprocal regulatory relationship between ENTs and autophagy.

Main Methods:

• Gene silencing (siRNA) to modulate SLC29A1 and SLC29A3 expression.
• Adenosine (Ado) treatment to assess transporter substrate effects.
• Western blotting to analyze PRKAA/AMPK phosphorylation and BECN1-BCL2 interaction.
• Pharmacological inhibition of SLC29A1 transport.
• Analysis of autophagy in prkaa-null cells and slc29a1^{- /-} / slc29a3^{- /-} mice.

Main Results:

• Cell surface SLC29A1/ENT1 inhibits autophagy by suppressing PRKAA/AMPK phosphorylation, contrasting with endolysosomal SLC29A3/ENT3's pro-autophagy role.
• Adenosine treatment induces PRKAA/AMPK-dependent autophagy, with SLC29A1 promoting adenosine efflux and attenuating this effect.
• SLC29A1 inhibits autophagosome formation by promoting BECN1-BCL2 interaction, independent of the MTOR pathway.
• Autophagy reciprocally regulates SLC29A1 and SLC29A3 expression, and corresponding mouse models exhibit altered autophagic activity.

Conclusions:

• SLC29A1 and SLC29A3 play distinct and opposing roles in autophagy regulation.
• SLC29A1's regulation of autophagy is dependent on its nucleoside transport function and cellular metabolic state.
• The findings reveal a dynamic, reciprocal relationship between ENTs and autophagy, offering therapeutic targets for related disorders.