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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 dispensable for the Cvt pathway and nonselective autophagy. (A) Atg37 is not required for the maturation of prApe1. Cells were grown in glucose medium (“Growth”) and then adapted to glucose medium without nitrogen for 6 h (“Starvation”). mApe1, mature Ape1; *, nonspecific band. (B) Atg37 is dispensable for cell survival during nitrogen starvation. Aliquots of cultures starved in glucose medium without nitrogen were plated on YPD medium. The number of cells able to form colonies was counted after 2–3 d of incubation. The data shown are from a single representative experiment out of two repeats. (C) Atg37 is not required for GFP-Atg8 processing by autophagy. Glucose-grown cells were adapted to glucose medium without nitrogen (SD-N).
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fig3: Atg37 is dispensable for the Cvt pathway and nonselective autophagy. (A) Atg37 is not required for the maturation of prApe1. Cells were grown in glucose medium (“Growth”) and then adapted to glucose medium without nitrogen for 6 h (“Starvation”). mApe1, mature Ape1; *, nonspecific band. (B) Atg37 is dispensable for cell survival during nitrogen starvation. Aliquots of cultures starved in glucose medium without nitrogen were plated on YPD medium. The number of cells able to form colonies was counted after 2–3 d of incubation. The data shown are from a single representative experiment out of two repeats. (C) Atg37 is not required for GFP-Atg8 processing by autophagy. Glucose-grown cells were adapted to glucose medium without nitrogen (SD-N).

Mentions: Despite a strong defect in pexophagy, Δatg37 cells were not affected in the maturation of the precursor of aminopeptidase I (prApe1) under both growth and starvation conditions (Fig. 3 A). At the same time, Δatg11 cells were blocked in the maturation of prApe1 only under growth conditions, Δatg28 cells showed partial maturation of prApe1 under both growth and starvation conditions, and pep4 prb1 cells, deficient in the vacuolar proteases A and B, were completely blocked in the maturation of prApe1 under both growth and starvation conditions, as expected (Farré et al., 2007; Nazarko et al., 2009). These results show that Atg37 is not required for the Cvt pathway and nonselective autophagy.


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 dispensable for the Cvt pathway and nonselective autophagy. (A) Atg37 is not required for the maturation of prApe1. Cells were grown in glucose medium (“Growth”) and then adapted to glucose medium without nitrogen for 6 h (“Starvation”). mApe1, mature Ape1; *, nonspecific band. (B) Atg37 is dispensable for cell survival during nitrogen starvation. Aliquots of cultures starved in glucose medium without nitrogen were plated on YPD medium. The number of cells able to form colonies was counted after 2–3 d of incubation. The data shown are from a single representative experiment out of two repeats. (C) Atg37 is not required for GFP-Atg8 processing by autophagy. Glucose-grown cells were adapted to glucose medium without nitrogen (SD-N).
© Copyright Policy - openaccess
Related In: Results  -  Collection

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

fig3: Atg37 is dispensable for the Cvt pathway and nonselective autophagy. (A) Atg37 is not required for the maturation of prApe1. Cells were grown in glucose medium (“Growth”) and then adapted to glucose medium without nitrogen for 6 h (“Starvation”). mApe1, mature Ape1; *, nonspecific band. (B) Atg37 is dispensable for cell survival during nitrogen starvation. Aliquots of cultures starved in glucose medium without nitrogen were plated on YPD medium. The number of cells able to form colonies was counted after 2–3 d of incubation. The data shown are from a single representative experiment out of two repeats. (C) Atg37 is not required for GFP-Atg8 processing by autophagy. Glucose-grown cells were adapted to glucose medium without nitrogen (SD-N).
Mentions: Despite a strong defect in pexophagy, Δatg37 cells were not affected in the maturation of the precursor of aminopeptidase I (prApe1) under both growth and starvation conditions (Fig. 3 A). At the same time, Δatg11 cells were blocked in the maturation of prApe1 only under growth conditions, Δatg28 cells showed partial maturation of prApe1 under both growth and starvation conditions, and pep4 prb1 cells, deficient in the vacuolar proteases A and B, were completely blocked in the maturation of prApe1 under both growth and starvation conditions, as expected (Farré et al., 2007; Nazarko et al., 2009). These results show that Atg37 is not required for the Cvt pathway and nonselective autophagy.

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