Journal: The FASEB Journal
Article Title: ULK2 is essential for degradation of ubiquitinated protein aggregates and homeostasis in skeletal muscle
doi: 10.1096/fj.201900766R
Figure Lengend Snippet: ULK2 is essential for skeletal muscle homeostasis. Our studies reveal that the Ulk2 gene presents a skeletal muscle–enriched pattern of expression in mice and that its deficiency in skeletal muscle, despite not impairing autophagy flux and proteolytic activities of the lysosome and proteasome, leads to robust accumulation of insoluble ubiquitinated protein aggregates associated with the adaptors p62 and NBR1. These findings suggest a key role for ULK2 in modulating the recognition and sequestration of ubiquitinated protein aggregates for degradation by autophagy (and potentially by the proteasome). The ensuing inability of ULK2-deficient muscle fibers to clear proteotoxic aggregates leads to atrophy, impaired force production, myofiber degeneration, and a generally unhealthy morphology of the muscle. Of note, these cellular events and functional outcomes are not observed in ULK1-deficient muscle. Autophagy is depicted with a phagophore and an autophagosome (white) and lysosome (blue).
Article Snippet: The following antibodies and respective dilutions were used for immunoblots: sequestosome 1 (SQSTM1) (p62) (P0067, 1:1000), ULK1 (A7481, 1:1000), FLAG (F1804, 1:1000) from MilliporeSigma, ULK2 (HPA009027, 1:500) from MilliporeSigma, next to breast cancer type 1 susceptibility protein gene 1 protein (NBR1) (sc-130380, 1:1000) from Santa Cruz Biotechnology (Dallas, TX, USA), LC3A/B (4108, 1:1000), ubiquitin (3936, 1:1000), cathepsin B (CTSB) (31718, 1:1000), lysosomal associated membrane protein 1 (LAMP1) (9091, 1:1000), autophagy related protein (Atg)13 (13273, 1:1000), Atg14 (5504, 1:1000), phosphorylated (p-)Atg14 (S29) (13155, 1:1000) from Cell Signaling Technology (Danvers, MA, USA), ULK2 (NBP1-33136, 1:500) from Novus Biologicals, p-p62 (S403) (MABC186-I, 1:1000) from MilliporeSigma, p-Atg13 (S318) (600-401-C49S, 1:1000) from Rockland (Limerick, PA, USA), and 20S (ab22673, 1:1000) from Abcam (Cambridge, United Kingdom).
Techniques: Expressing, Functional Assay
