TBC1D14 regulates autophagosome formation via Rab11- and ULK1-positive recycling endosomes

Abstract

The noncatalytic RabGAP protein TBC1D14 regulates the Rab11- and ULK1-positive recycling endosomes required for autophagosome formation upon starvation

SNX 18 regulates ATG 9A trafficking from recycling endosomes by recruiting Dynamin‐2

“…TBC1D14 is a RAB11 effector protein and is known to regulate autophagy and ATG9A trafficking via binding to the TRAPP complex 8, 11. It was found that proper ATG9A traffic between recycling endosomes and the Golgi apparatus depends on the generation of a tubular intermediate membrane compartment containing ATG9A, where a switch between RAB11 and RAB1 occurs and is facilitated by a TBC1D14‐TRAPPIII‐like complex.…”

“…DyLight‐680‐ and DyLight‐800‐conjugated secondary antibodies were obtained from Invitrogen (SA5‐10170 and SA5‐10044, 1:5,000). Antibodies used for immunofluorescence are as follows: mouse anti‐WIPI2 (from Sharon Tooze 40, 1:2,000), rabbit anti‐ATG16L1 (MBL, PM040, 1:200), hamster anti‐ATG9A (from Sharon Tooze 41, 1:1,000), rabbit anti‐ATG9A (Abcam, ab108338, 1:400), mouse anti‐myc (IF and WB—DSHB, cl9E10, 1:20), rabbit anti‐TBC1D14 (from Sharon Tooze 8, 1:200), chicken anti‐SNX18 (from Sven Carlsson, 26, 30, 1:200), goat anti‐myc (Abcam, ab9132, 1:500), mouse anti‐TfR (Santa Cruz Biotechnology, sc‐65877, 1:200), mouse anti‐Dynamin (Upstate/Millipore, 05‐319, 1:100). Alexa 488‐conjugated secondary antibodies were obtained from Invitrogen (A‐21206 and A‐21202, 1:500), and Cy3 and Cy5‐conjugated secondary antibodies were obtained from Jackson ImmunoResearch (Cy3: 715‐165‐151, 127‐165‐099 and 711‐165‐152, Cy5: 711‐495‐152 and 715‐175‐150).…”

“…The PI3P‐binding protein WIPI2 is recruited to the forming phagophore 3 where it further interacts with the ATG12–5‐16L1 complex to allow conjugation of Atg8 homologues of the LC3 and GABARAP subfamilies to phosphatidylethanolamine (PE) in the autophagic membrane 4, 5. Mammalian ATG9A is the only conserved transmembrane core ATG protein and has been found to localise to the trans‐Golgi network (TGN), plasma membrane and endosomes, including recycling endosomes 6, 7, 8, 9, 10. ATG9A cycles between these compartments and the continuous trafficking of ATG9A are thought to generate an ATG9A reservoir ready to contribute to autophagosome biogenesis upon induction of autophagy 10, 11, 12.…”

“…The phagophore expands by receiving membrane input through vesicle transport or membrane contact sites from different membrane sources, including ER‐exit sites (ERES) and the ER–Golgi intermediate compartment (ERGIC) 18, 19, 20, the Golgi apparatus 21, 22, mitochondria 23, 24 and the plasma membrane 21, 22, 25. Recently, it has become evident that recycling endosomes also play an important role during autophagosome biogenesis and both ATG16L1 and ATG9A traffic from the plasma membrane to recycling endosomes on their way to sites of autophagosome formation 7, 8, 9, 10, 26. We recently identified the PX‐BAR‐containing protein sorting nexin 18 (SNX18) as a positive regulator of autophagy 26.…”

A current perspective of autophagosome biogenesis

“…Although TBC1D14 has a putative RabGAP domain, it does not appear to have RabGAP activity for Rab11, instead it may act as a downstream effector of Rab11. Overexpression of TBC1D14 negatively regulates autophagy possibly by sequestering the ULK1 complex in the recycling endosome through the direct binding between TBC1D14 and ULK1 [86].…”