Interaction of caveolin-1 with ATG12-ATG5 system suppresses autophagy in lung epithelial cells

Abstract

AM, Shen H. Interaction of caveolin-1 with ATG12-ATG5 system suppresses autophagy in lung epithelial cells. Am J Physiol Lung Cell Mol Physiol 306: L1016 -L1025, 2014. First published April 11, 2014 doi:10.1152/ajplung.00268.2013.-Autophagy plays a pivotal role in cellular homeostasis and adaptation to adverse environments, although the regulation of this process remains incompletely understood. We have recently observed that caveolin-1 (Cav-1), a major constituent of lipid rafts on plasma membrane, can regulate autophagy in cigarette smoking-induced injury of lung epithelium, although the underlying molecular mechanisms remain incompletely understood. In the present study we found that Cav-1 interacted with and regulated the expression of ATG12-ATG5, an ubiquitin-like conjugation system crucial for autophagosome formation, in lung epithelial Beas-2B cells. Deletion of Cav-1 increased basal and starvation-induced levels of ATG12-ATG5 and autophagy. Biochemical analyses revealed that Cav-1 interacted with ATG5, ATG12, and their active complex ATG12-ATG5. Overexpression of ATG5 or ATG12 increased their interactions with Cav-1, the formation of ATG12-ATG5 conjugate, and the subsequent basal levels of autophagy but resulted in decreased interactions between Cav-1 and another molecule. Knockdown of ATG12 enhanced the ATG5-Cav-1 interaction. Mutation of the Cav-1 binding motif on ATG12 disrupted their interaction and further augmented autophagy. Cav-1 also regulated the expression of ATG16L, another autophagy protein associating with the ATG12-ATG5 conjugate during autophagosome formation. Altogether these studies clearly demonstrate that Cav-1 competitively interacts with the ATG12-ATG5 system to suppress the formation and function of the latter in lung epithelial cells, thereby providing new insights into the molecular mechanisms by which Cav-1 regulates autophagy and suggesting the important function of Cav-1 in certain lung diseases via regulation of autophagy homeostasis.caveolin-1; ATG12-ATG5; ATG16L; autophagy; lung diseases AUTOPHAGY IS A DYNAMIC PROCESS responsible for the turnover of cellular organelles and long-lived proteins. During this process, cytosolic proteins and organelles (e.g., mitochondria and endoplasmic reticulum) are engulfed into double-membranebound vesicles, autophagosomes. The outer membrane of the autophagosome subsequently fuses with lysosomes to form autolysosomes in which the engulfed components are degraded by lysosomal hydrolases, regenerating metabolic precursors that are recycled for macromolecular synthesis and ATP generation (20, 42). Autophagy is induced above basal levels in response to diverse stimuli including nutrient starvation, genotoxic agents, cytokines, and oxidative stress. This process provides an essential function in the maintenance of cellular homeostasis and adaptation to adverse environments (16,29,35).More than 30 autophagy-related genes and gene products critical in the regulation of autophagy, designated "ATG," have been identified heretofore in yeast and hi...

PRNP/prion protein regulates the secretion of exosomes modulating CAV1/caveolin-1-suppressed autophagy

“…6A and C), which is involved in expansion of the phagophore, and is negatively regulated by CAV1. 46 Remarkably, restoration of full-length PRNP or PRNP lacking the hydrophobic domain rescued the ability of prnp 0/0 cells to secrete exosomes (Fig. 6D).…”

“…9,49 Interestingly, CAV1 impairs the interaction between ATG5 and ATG12 in the cytoplasm, thereby suppressing autophagy. 46 We thus investigated if CAV1 is affected by PRNP expression.…”

Tyrosine kinase receptor EGFR regulates the switch in cancer cells between cell survival and cell death induced by autophagy in hypoxia

“…9D). Previous studies showed that CAV1 interacted with the autophagy ATG12-ATG5 protein complex 43 and LC3B 44 suggesting that CAV1 can be degraded by autophagy. We then knocked down autophagy genes ATG5 and BECN1 in A549 cells and found that the CAV1 protein level in hypoxia increased (Fig.…”

Caveolin-1 contributes to realgar nanoparticle therapy in human chronic myelogenous leukemia K562 cells

“…Therefore, K562 cells were transiently transfected with Cav-1 overexpression plasmid (Cav-1 OE) or negative control plasmid (Cav-1 NC) for the following research. After being 24,48, and 72 h, the cells were harvested, respectively, and subjected to Western blot analysis. Compared with Cav-1 NC group, the level of Cav-1 expression was significantly increased at 24, 48, and 72 h after being transfected with Cav-1 overexpression plasmid ( Figure 6C).…”

“…21 Recently, several studies have shown that autophagy is associated with Cav-1. [22][23][24] Furthermore, we have found that Cav-1 is involved in the autophagy process induced by realgar NPs in human hepatocellular carcinoma cells in our previous work. 25 However, the mechanism of realgar NPs in treating CML and whether Cav-1 participates in therapy-induced CML cells death remain unclear.…”