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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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Atg37 is required for pexophagy at the stage of phagophore formation. (A) Atg37 is expressed strictly under peroxisome proliferation conditions. Glc, glucose medium; Eth, ethanol medium; Mth, methanol medium; Ole, oleate medium; F1β, loading control. (B and C) Atg37 is dispensable for peroxisome biogenesis. Peroxisome biogenesis was assessed by the growth of strains in methanol (B) and oleate (C) media. The data shown are from a single representative experiment out of two repeats. (D and E) Atg37 is required for micropexophagy (D) and macropexophagy (E). Cells were replica plated from methanol to glucose and ethanol plates, respectively. The residual activity of AOX was used to assess pexophagy. (F and G) Atg37 is needed for the delivery of peroxisomes to the vacuole during micropexophagy (F) and macropexophagy (G). Methanol-grown cells were adapted to glucose and ethanol media, respectively. FM 4-64 labeled vacuolar membranes. Arrows point to the WT vacuoles with the peroxisome-associated GFP-SKL. Bars, 5 µm. (H and I) Atg37 is essential for MIPA (H) and pexophagosome (I) formation during micropexophagy and macropexophagy, respectively. Methanol-grown cells were adapted to glucose and ethanol media. Arrows point to MIPA (H) and pexophagosome (I) in the WT cells. Bars, 5 µm.
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fig2: Atg37 is required for pexophagy at the stage of phagophore formation. (A) Atg37 is expressed strictly under peroxisome proliferation conditions. Glc, glucose medium; Eth, ethanol medium; Mth, methanol medium; Ole, oleate medium; F1β, loading control. (B and C) Atg37 is dispensable for peroxisome biogenesis. Peroxisome biogenesis was assessed by the growth of strains in methanol (B) and oleate (C) media. The data shown are from a single representative experiment out of two repeats. (D and E) Atg37 is required for micropexophagy (D) and macropexophagy (E). Cells were replica plated from methanol to glucose and ethanol plates, respectively. The residual activity of AOX was used to assess pexophagy. (F and G) Atg37 is needed for the delivery of peroxisomes to the vacuole during micropexophagy (F) and macropexophagy (G). Methanol-grown cells were adapted to glucose and ethanol media, respectively. FM 4-64 labeled vacuolar membranes. Arrows point to the WT vacuoles with the peroxisome-associated GFP-SKL. Bars, 5 µm. (H and I) Atg37 is essential for MIPA (H) and pexophagosome (I) formation during micropexophagy and macropexophagy, respectively. Methanol-grown cells were adapted to glucose and ethanol media. Arrows point to MIPA (H) and pexophagosome (I) in the WT cells. Bars, 5 µm.

Mentions: To gain insight into the function of Atg37, we studied its expression profile. Like many peroxins, Atg37 was repressed in glucose and ethanol media, but induced under peroxisome proliferation conditions in methanol and oleate media (Fig. 2 A). While cells lacking most peroxins, such as Δpex3 cells, fail to grow under peroxisome proliferation conditions, Δatg37 cells grew normally in both methanol and oleate media (Fig. 2, B and C), which suggests that Atg37 is not required for peroxisome biogenesis. We hypothesized that it might be required for 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)

Atg37 is required for pexophagy at the stage of phagophore formation. (A) Atg37 is expressed strictly under peroxisome proliferation conditions. Glc, glucose medium; Eth, ethanol medium; Mth, methanol medium; Ole, oleate medium; F1β, loading control. (B and C) Atg37 is dispensable for peroxisome biogenesis. Peroxisome biogenesis was assessed by the growth of strains in methanol (B) and oleate (C) media. The data shown are from a single representative experiment out of two repeats. (D and E) Atg37 is required for micropexophagy (D) and macropexophagy (E). Cells were replica plated from methanol to glucose and ethanol plates, respectively. The residual activity of AOX was used to assess pexophagy. (F and G) Atg37 is needed for the delivery of peroxisomes to the vacuole during micropexophagy (F) and macropexophagy (G). Methanol-grown cells were adapted to glucose and ethanol media, respectively. FM 4-64 labeled vacuolar membranes. Arrows point to the WT vacuoles with the peroxisome-associated GFP-SKL. Bars, 5 µm. (H and I) Atg37 is essential for MIPA (H) and pexophagosome (I) formation during micropexophagy and macropexophagy, respectively. Methanol-grown cells were adapted to glucose and ethanol media. Arrows point to MIPA (H) and pexophagosome (I) in the WT cells. Bars, 5 µm.
© Copyright Policy - openaccess
Related In: Results  -  Collection

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

fig2: Atg37 is required for pexophagy at the stage of phagophore formation. (A) Atg37 is expressed strictly under peroxisome proliferation conditions. Glc, glucose medium; Eth, ethanol medium; Mth, methanol medium; Ole, oleate medium; F1β, loading control. (B and C) Atg37 is dispensable for peroxisome biogenesis. Peroxisome biogenesis was assessed by the growth of strains in methanol (B) and oleate (C) media. The data shown are from a single representative experiment out of two repeats. (D and E) Atg37 is required for micropexophagy (D) and macropexophagy (E). Cells were replica plated from methanol to glucose and ethanol plates, respectively. The residual activity of AOX was used to assess pexophagy. (F and G) Atg37 is needed for the delivery of peroxisomes to the vacuole during micropexophagy (F) and macropexophagy (G). Methanol-grown cells were adapted to glucose and ethanol media, respectively. FM 4-64 labeled vacuolar membranes. Arrows point to the WT vacuoles with the peroxisome-associated GFP-SKL. Bars, 5 µm. (H and I) Atg37 is essential for MIPA (H) and pexophagosome (I) formation during micropexophagy and macropexophagy, respectively. Methanol-grown cells were adapted to glucose and ethanol media. Arrows point to MIPA (H) and pexophagosome (I) in the WT cells. Bars, 5 µm.
Mentions: To gain insight into the function of Atg37, we studied its expression profile. Like many peroxins, Atg37 was repressed in glucose and ethanol media, but induced under peroxisome proliferation conditions in methanol and oleate media (Fig. 2 A). While cells lacking most peroxins, such as Δpex3 cells, fail to grow under peroxisome proliferation conditions, Δatg37 cells grew normally in both methanol and oleate media (Fig. 2, B and C), which suggests that Atg37 is not required for peroxisome biogenesis. We hypothesized that it might be required for 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