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Peroxisomal Atg37 binds Atg30 or palmitoyl-CoA to regulate phagophore formation during pexophagy.

Nazarko TY, Ozeki K, Till A, Ramakrishnan G, Lotfi P, Yan M, Subramani S - J. Cell Biol. (2014)

Bottom Line: Palmitoyl-CoA competes with Atg30 for Atg37 binding.The human orthologue of Atg37, acyl-CoA-binding domain containing protein 5 (ACBD5), is also peroxisomal and is required specifically for pexophagy.We suggest that Atg37/ACBD5 is a new component and positive regulator of the pexophagic RPC.

View Article: PubMed Central - HTML - PubMed

Affiliation: Section of Molecular Biology, Division of Biological Sciences, and 2 San Diego Center for Systems Biology, University of California, San Diego, La Jolla, CA 92093.

ABSTRACT
Autophagy is a membrane trafficking pathway that sequesters proteins and organelles into autophagosomes. The selectivity of this pathway is determined by autophagy receptors, such as the Pichia pastoris autophagy-related protein 30 (Atg30), which controls the selective autophagy of peroxisomes (pexophagy) through the assembly of a receptor protein complex (RPC). However, how the pexophagic RPC is regulated for efficient formation of the phagophore, an isolation membrane that sequesters the peroxisome from the cytosol, is unknown. Here we describe a new, conserved acyl-CoA-binding protein, Atg37, that is an integral peroxisomal membrane protein required specifically for pexophagy at the stage of phagophore formation. Atg30 recruits Atg37 to the pexophagic RPC, where Atg37 regulates the recruitment of the scaffold protein, Atg11. Palmitoyl-CoA competes with Atg30 for Atg37 binding. The human orthologue of Atg37, acyl-CoA-binding domain containing protein 5 (ACBD5), is also peroxisomal and is required specifically for pexophagy. We suggest that Atg37/ACBD5 is a new component and positive regulator of the pexophagic RPC.

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Atg30 requires Atg37 for recruitment of Atg11 to the pexophagic RPC. (A) Atg37 is required for pexophagy induced by the overexpression of Atg30. (B) Atg37 is necessary for the growth suppression in methanol medium caused by the overexpression of Atg30. The data shown are from a single representative experiment out of two repeats. (C) Atg11 does not coimmunoprecipitate with Atg30 in the absence of Atg37. Methanol-grown cells were adapted to the glucose medium without nitrogen for 0.5 h. The results are presented for two independent colonies of Δatg37. *, nonspecific band. (D) Atg37 is required for the Atg30-dependent localization of Atg11 to the proximity of peroxisomes. Methanol-grown cells were adapted to the glucose medium without nitrogen for 1 h. Arrows point to the accumulation of GFP-Atg11 near the peroxisomes in WT cells and on the vacuolar membrane in the mutant cells. Bar, 5 µm.
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fig6: Atg30 requires Atg37 for recruitment of Atg11 to the pexophagic RPC. (A) Atg37 is required for pexophagy induced by the overexpression of Atg30. (B) Atg37 is necessary for the growth suppression in methanol medium caused by the overexpression of Atg30. The data shown are from a single representative experiment out of two repeats. (C) Atg11 does not coimmunoprecipitate with Atg30 in the absence of Atg37. Methanol-grown cells were adapted to the glucose medium without nitrogen for 0.5 h. The results are presented for two independent colonies of Δatg37. *, nonspecific band. (D) Atg37 is required for the Atg30-dependent localization of Atg11 to the proximity of peroxisomes. Methanol-grown cells were adapted to the glucose medium without nitrogen for 1 h. Arrows point to the accumulation of GFP-Atg11 near the peroxisomes in WT cells and on the vacuolar membrane in the mutant cells. Bar, 5 µm.

Mentions: Formation of the phagophore around the peroxisome is a multistep process initiated by the pexophagy receptor, Atg30, via formation of the RPC. To find the role of Atg37 in this process, we first positioned the function of Atg37 relative to Atg30. As mentioned above, overexpression of Atg30 can induce pexophagy in methanol medium, which is disadvantageous for cell growth due to the degradation of peroxisomes required for methanol utilization (Farré et al., 2008). We found that Atg37 is required for this process, as the levels of Pex3, Pex12, and even of Atg30-GFP itself were considerably higher in the Δatg37 mutant than in WT cells, when Atg30-GFP was overexpressed from the promoter of the GAPDH gene (Fig. 6 A). Deletion of the ATG37 gene also improved the growth of the strain overexpressing Atg30-GFP in methanol medium (Fig. 6 B), which suggests that Atg37 acts downstream of Atg30 in pexophagy.


Peroxisomal Atg37 binds Atg30 or palmitoyl-CoA to regulate phagophore formation during pexophagy.

Nazarko TY, Ozeki K, Till A, Ramakrishnan G, Lotfi P, Yan M, Subramani S - J. Cell Biol. (2014)

Atg30 requires Atg37 for recruitment of Atg11 to the pexophagic RPC. (A) Atg37 is required for pexophagy induced by the overexpression of Atg30. (B) Atg37 is necessary for the growth suppression in methanol medium caused by the overexpression of Atg30. The data shown are from a single representative experiment out of two repeats. (C) Atg11 does not coimmunoprecipitate with Atg30 in the absence of Atg37. Methanol-grown cells were adapted to the glucose medium without nitrogen for 0.5 h. The results are presented for two independent colonies of Δatg37. *, nonspecific band. (D) Atg37 is required for the Atg30-dependent localization of Atg11 to the proximity of peroxisomes. Methanol-grown cells were adapted to the glucose medium without nitrogen for 1 h. Arrows point to the accumulation of GFP-Atg11 near the peroxisomes in WT cells and on the vacuolar membrane in the mutant cells. Bar, 5 µm.
© Copyright Policy - openaccess
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC3926955&req=5

fig6: Atg30 requires Atg37 for recruitment of Atg11 to the pexophagic RPC. (A) Atg37 is required for pexophagy induced by the overexpression of Atg30. (B) Atg37 is necessary for the growth suppression in methanol medium caused by the overexpression of Atg30. The data shown are from a single representative experiment out of two repeats. (C) Atg11 does not coimmunoprecipitate with Atg30 in the absence of Atg37. Methanol-grown cells were adapted to the glucose medium without nitrogen for 0.5 h. The results are presented for two independent colonies of Δatg37. *, nonspecific band. (D) Atg37 is required for the Atg30-dependent localization of Atg11 to the proximity of peroxisomes. Methanol-grown cells were adapted to the glucose medium without nitrogen for 1 h. Arrows point to the accumulation of GFP-Atg11 near the peroxisomes in WT cells and on the vacuolar membrane in the mutant cells. Bar, 5 µm.
Mentions: Formation of the phagophore around the peroxisome is a multistep process initiated by the pexophagy receptor, Atg30, via formation of the RPC. To find the role of Atg37 in this process, we first positioned the function of Atg37 relative to Atg30. As mentioned above, overexpression of Atg30 can induce pexophagy in methanol medium, which is disadvantageous for cell growth due to the degradation of peroxisomes required for methanol utilization (Farré et al., 2008). We found that Atg37 is required for this process, as the levels of Pex3, Pex12, and even of Atg30-GFP itself were considerably higher in the Δatg37 mutant than in WT cells, when Atg30-GFP was overexpressed from the promoter of the GAPDH gene (Fig. 6 A). Deletion of the ATG37 gene also improved the growth of the strain overexpressing Atg30-GFP in methanol medium (Fig. 6 B), which suggests that Atg37 acts downstream of Atg30 in pexophagy.

Bottom Line: Palmitoyl-CoA competes with Atg30 for Atg37 binding.The human orthologue of Atg37, acyl-CoA-binding domain containing protein 5 (ACBD5), is also peroxisomal and is required specifically for pexophagy.We suggest that Atg37/ACBD5 is a new component and positive regulator of the pexophagic RPC.

View Article: PubMed Central - HTML - PubMed

Affiliation: Section of Molecular Biology, Division of Biological Sciences, and 2 San Diego Center for Systems Biology, University of California, San Diego, La Jolla, CA 92093.

ABSTRACT
Autophagy is a membrane trafficking pathway that sequesters proteins and organelles into autophagosomes. The selectivity of this pathway is determined by autophagy receptors, such as the Pichia pastoris autophagy-related protein 30 (Atg30), which controls the selective autophagy of peroxisomes (pexophagy) through the assembly of a receptor protein complex (RPC). However, how the pexophagic RPC is regulated for efficient formation of the phagophore, an isolation membrane that sequesters the peroxisome from the cytosol, is unknown. Here we describe a new, conserved acyl-CoA-binding protein, Atg37, that is an integral peroxisomal membrane protein required specifically for pexophagy at the stage of phagophore formation. Atg30 recruits Atg37 to the pexophagic RPC, where Atg37 regulates the recruitment of the scaffold protein, Atg11. Palmitoyl-CoA competes with Atg30 for Atg37 binding. The human orthologue of Atg37, acyl-CoA-binding domain containing protein 5 (ACBD5), is also peroxisomal and is required specifically for pexophagy. We suggest that Atg37/ACBD5 is a new component and positive regulator of the pexophagic RPC.

Show MeSH
Related in: MedlinePlus