Autophagy is essential for the maintenance of cellular homeostasis and its dysfunction has been linked to various diseases. Autophagy is a membrane driven process and tightly regulated by ...membrane-associated proteins. Here, we summarized membrane lipid composition, and membrane-associated proteins relevant to autophagy from a spatiotemporal perspective. In particular, we focused on three important membrane remodeling processes in autophagy, lipid transfer for phagophore elongation, membrane scission for phagophore closure, and autophagosome-lysosome membrane fusion. We discussed the significance of the discoveries in this field and possible avenues to follow for future studies. Finally, we summarized the membrane-associated biochemical techniques and assays used to study membrane properties, with a discussion of their applications in autophagy.
Autophagy is crucial for degrading and recycling cellular components. Fusion between autophagosomes and lysosomes is pivotal, directing autophagic cargo to degradation. This process is driven by ...STX17-SNAP29-VAMP8 and STX7-SNAP29-YKT6 in mammalian cells. However, the interaction between STX17 and YKT6 and its significance remain to be revealed. In this study, we challenge the notion that STX17 and YKT6 function independently in autophagosome-lysosome fusion. YKT6, through its SNARE domain, forms a complex with STX17 and SNAP29 on autophagosomes, enhancing autophagy flux. VAMP8 displaces YKT6 from this complex, leading to the formation of the fusogenic complex STX17-SNAP29-VAMP8. We demonstrated that the YKT6-SNAP29-STX17 complex facilitates both lipid and content mixing driven by STX17-SNAP29-VAMP8, suggesting a priming role of YKT6 for efficient membrane fusion. Our results provide a potential regulation mechanism of autophagosome-lysosome fusion, highlighting the importance of YKT6 and its interactions with STX17 and SNAP29 in promoting autophagy flux.
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•YKT6 cooperates rather than competes with STX17 in complexing with SNAP29•YKT6 forms a priming complex with STX17 and SNAP29 on autophagosomes•This priming complex promotes autophagosome-lysosome fusion mediated by STX17-SNAP29-VAMP8
Zheng et al. show that YKT6 forms a priming complex with STX17 and SNAP29 on autophagosomes to facilitate autophagosome-lysosome fusion, mediated by STX17-SNAP29-VAMP8. This finding challenges the prevailing notion that STX17-SNAP29-VAMP8 and STX7-SNAP29-YKT6 are two parallel SNARE complexes mediating autophagosome-lysosome fusion and demonstrates another function of YKT6 in autophagosome-lysosome fusion.
Abstract
The multi-subunit homotypic fusion and vacuole protein sorting (HOPS) membrane-tethering complex is required for autophagosome-lysosome fusion in mammals, yet reconstituting the mammalian ...HOPS complex remains a challenge. Here we propose a “hook-up” model for mammalian HOPS complex assembly, which requires two HOPS sub-complexes docking on membranes via membrane-associated Rabs. We identify Rab39A as a key small GTPase that recruits HOPS onto autophagic vesicles. Proper pairing with Rab2 and Rab39A enables HOPS complex assembly between proteoliposomes for its tethering function, facilitating efficient membrane fusion. GTP loading of Rab39A is important for the recruitment of HOPS to autophagic membranes. Activation of Rab39A is catalyzed by C9orf72, a guanine exchange factor associated with amyotrophic lateral sclerosis and familial frontotemporal dementia. Constitutive activation of Rab39A can rescue autophagy defects caused by C9orf72 depletion. These results therefore reveal a crucial role for the C9orf72-Rab39A-HOPS axis in autophagosome-lysosome fusion.
Macroautophagy is a process that cells engulf cytosolic materials by autophagosomes and deliver them to lysosomes for degradation. The biogenesis of autophagosomes requires ATG2 as a lipid transfer ...protein to transport lipids from existing membranes to phagophores. It is generally believed that endoplasmic reticulum is the main source for lipid supply of the forming autophagosomes; whether ATG2 can transfer lipids from other organelles to phagophores remains elusive. In this study, we identified a new ATG2A-binding protein, ANKFY1. Depletion of this endosome-localized protein led to the impaired autophagosome growth and the reduced autophagy flux, which largely phenocopied ATG2A/B depletion. A pool of ANKFY1 co-localized with ATG2A between endosomes and phagophores and depletion of UVRAG, ANKFY1 or ATG2A/B led to reduction of PI3P distribution on phagophores. Purified recombinant ANKFY1 bound to PI3P on membrane through its FYVE domain and enhanced ATG2A-mediated lipid transfer between PI3P-containing liposomes. Therefore, we propose that ANKFY1 recruits ATG2A to PI3P-enriched endosomes and promotes ATG2A-mediated lipid transfer from endosomes to phagophores. This finding implicates a new lipid source for ATG2A-mediated phagophore expansion, where endosomes donate PI3P and other lipids to phagophores via lipid transfer.
To demonstrate the effects of a newly designed postural alignment relearning system on postural control dysfunction in a typical patient with cerebral palsy (CP).
Evaluation before and after 8 weeks ...of Constraint Standing Training 3-dimensional postural alignment relearning system.
Department of Rehabilitation Medicine.
A 6-year-old girl with CP and postural misalignment on Gross Motor Function Classification System level I.
Constraint Standing Training for 8 weeks to correct postural misalignment.
Parameters of lateral plain radiographs in static standing, posturography measurements in standing and walking, motor ability (Gross Motor Function Measure-88 GMFM-88 scores, manual muscle testing MMT scores, muscle architecture), and gait kinematic parameters (40 3-dimensional parameters of arms, trunk, waist, and lower limbs).
Knee hyperextension angle in static standing; peaks of knee flexion angle (KFA) when walking, hip flexion angle and ankle flexion angle in dynamic standing; and the KFA at initial contact in gait cycle all decreased significantly (P<.01). Scores of GMFM-88 sections D and E and MMT of 5 core stability muscles improved (P<.01). The velocities and range of motion of the arms, the 3-dimensinoal range of motion of the trunk and waist, and most of the parameters of the lower limbs showed statistically significant change (P<.01). Bilateral muscle thickness did not change significantly after the treatment (P=.738 left, P=.978 right), but the gluteus maximus morphology was changed: the muscle fibers became rounder, the interfiber space decreased, and the border lines of the muscle fibers got clearer.
Postural alignment, motor ability, and gait may be homologous external manifestations of more fundamental core abilities, referring to correct standing posture cognition, muscle activation, and postural unconsciousness. Constraint Standing Training 3-dimensional postural alignment relearning system aimed to improve the static and dynamic standing control ability, may fix postural misalignment and improve motor ability and flexed-knee gait. Future work should use Constraint Standing Training with patients with different kinds of misalignment, choose sensitive indicators, observe the duration of each step, and reveal the mechanism causes postural misalignment.
By a wide analysis on examination papers within exam cheating, we found that the main cause of test cheating is the paper and the environment which makes exam cheating possible for students. Based on ...Extenics and information technology, we presented several systemic solutions, one is to design an individual examination paper, its answer depends on individual's personal information; another is to test on computers with a support of monitor software. Furthermore, we put forward some extension solutions. The applications in Chinese universities have approved its effectiveness.
OBJECTIVETo demonstrate the effects of a newly designed postural alignment relearning system on postural control dysfunction in a typical patient with cerebral palsy (CP). DESIGNEvaluation before and ...after 8 weeks of Constraint Standing Training 3-dimensional postural alignment relearning system. SETTINGDepartment of Rehabilitation Medicine. PARTICIPANTA 6-year-old girl with CP and postural misalignment on Gross Motor Function Classification System level I. INTERVENTIONSConstraint Standing Training for 8 weeks to correct postural misalignment. MAIN OUTCOME MEASURESParameters of lateral plain radiographs in static standing, posturography measurements in standing and walking, motor ability (Gross Motor Function Measure-88 GMFM-88 scores, manual muscle testing MMT scores, muscle architecture), and gait kinematic parameters (40 3-dimensional parameters of arms, trunk, waist, and lower limbs). RESULTSKnee hyperextension angle in static standing; peaks of knee flexion angle (KFA) when walking, hip flexion angle and ankle flexion angle in dynamic standing; and the KFA at initial contact in gait cycle all decreased significantly (P<.01). Scores of GMFM-88 sections D and E and MMT of 5 core stability muscles improved (P<.01). The velocities and range of motion of the arms, the 3-dimensinoal range of motion of the trunk and waist, and most of the parameters of the lower limbs showed statistically significant change (P<.01). Bilateral muscle thickness did not change significantly after the treatment (P=.738 left, P=.978 right), but the gluteus maximus morphology was changed: the muscle fibers became rounder, the interfiber space decreased, and the border lines of the muscle fibers got clearer. CONCLUSIONSPostural alignment, motor ability, and gait may be homologous external manifestations of more fundamental core abilities, referring to correct standing posture cognition, muscle activation, and postural unconsciousness. Constraint Standing Training 3-dimensional postural alignment relearning system aimed to improve the static and dynamic standing control ability, may fix postural misalignment and improve motor ability and flexed-knee gait. Future work should use Constraint Standing Training with patients with different kinds of misalignment, choose sensitive indicators, observe the duration of each step, and reveal the mechanism causes postural misalignment.
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