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Defective autophagy is a key feature of cerebral cavernous malformations.

Marchi S, Corricelli M, Trapani E, Bravi L, Pittaro A, Delle Monache S, Ferroni L, Patergnani S, Missiroli S, Goitre L, Trabalzini L, Rimessi A, Giorgi C, Zavan B, Cassoni P, Dejana E, Retta SF, Pinton P - EMBO Mol Med (2015)

Bottom Line: KRIT1 loss-of-function activates the mTOR-ULK1 pathway, which is a master regulator of autophagy, and treatment with mTOR inhibitors rescues some of the mole-cular and cellular phenotypes associated with CCM.Furthermore, defective autophagy is highly correlated to endothelial-to-mesenchymal transition, a crucial event that contributes to CCM progression.Taken together, our data point to a key role for defective autophagy in CCM disease pathogenesis, thus providing a novel framework for the development of new pharmacological strategies to prevent or reverse adverse clinical outcomes of CCM lesions.

View Article: PubMed Central - PubMed

Affiliation: Department of Morphology, Surgery and Experimental Medicine, Section of Pathology Oncology and Experimental Biology, University of Ferrara, Ferrara, Italy.

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KRIT1-ablated cells display autophagy suppressionImmunoblot analysis of p62 and LC3 I/II in KRIT1 wt and KRIT1-KO endothelial cells. Actin was used as a loading control. Quantification of total LC3 on actin is reported (*P = 0.02712). The results are representative of three independent experiments.Representative images of p62 dots in KRIT1 wt and KRIT1-KO endothelial cells. Scale bar, 20 μm. Magnifications in insets. Right, quantitative analysis of p62 distribution of dots is reported (four independent experiments; n = 35 cells per group). *P = 0.00542 (dotted); *P = 0.00014 (nuclear).Immunoblot analysis of p62 and LC3 I/II in KRIT1-KO and KRIT1-KO re-expressing KRIT1 (KO+KRIT1) MEFs. Left, immunoblot showing KRIT1 levels in KRIT1-KO and KO+KRIT1 cells. Right, immunoblots for p62 and LC3 I/II. Actin was used as a loading marker. Quantification of total LC3 on actin is reported (*P = 0.01248). The results are representative of three independent experiments.Representative images of p62 dots in KO+KRIT1 (top) and KRIT1-KO cells (bottom). Scale bar, 50 μm. Magnifications in insets. Right, quantitative analysis of the number of p62 dots per cell is shown (four independent experiments; n = 50 cells per group). *P = 7.18e−14.Immunoblot analysis of hBMECs transiently transfected with control siRNA or KRIT1 siRNA. Left, evaluation of siRNA efficiency with antibody directed against KRIT1. Right, immunoblots for p62 and LC3 I/II. Actin was used as a loading marker. Quantification of total LC3 on actin is reported (*P = 0.03071). The results are representative of three independent experiments.Immunoblot analysis of EA.hy926 cells transiently transfected with control siRNA or KRIT1 siRNA. Left, evaluation of siRNA efficiency with antibody directed against KRIT1. Right, immunoblot for p62 and LC3 I/II. Actin was used as a loading marker. Quantification of total LC3 on actin is reported (*P = 0.02527). The results are representative of three independent experiments.Immunofluorescence analysis of p62 (green) and ProteoStat Aggresome staining detection reagent (red) in KRIT1 wt and KRIT1-KO lung endothelial cells. The yellow signal in the merged images represents an overlapping spatial relationship between green and red fluorescence. Magnification in insets. Scale bar, 50 μm. The images are representative of four independent experiments.Immunofluorescence analysis of p62 (green) and ProteoStat Aggresome staining detection reagent (red) in KRIT1-KO re-expressing KRIT1 (KO+KRIT1) and KRIT1-KO MEFs. The yellow signal in the merged images represents an overlapping spatial relationship between green and red fluorescence. Magnification in insets. Scale bar, 50 μm. The images are representative of four independent experiments.Source data are available online for this figure.
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fig01: KRIT1-ablated cells display autophagy suppressionImmunoblot analysis of p62 and LC3 I/II in KRIT1 wt and KRIT1-KO endothelial cells. Actin was used as a loading control. Quantification of total LC3 on actin is reported (*P = 0.02712). The results are representative of three independent experiments.Representative images of p62 dots in KRIT1 wt and KRIT1-KO endothelial cells. Scale bar, 20 μm. Magnifications in insets. Right, quantitative analysis of p62 distribution of dots is reported (four independent experiments; n = 35 cells per group). *P = 0.00542 (dotted); *P = 0.00014 (nuclear).Immunoblot analysis of p62 and LC3 I/II in KRIT1-KO and KRIT1-KO re-expressing KRIT1 (KO+KRIT1) MEFs. Left, immunoblot showing KRIT1 levels in KRIT1-KO and KO+KRIT1 cells. Right, immunoblots for p62 and LC3 I/II. Actin was used as a loading marker. Quantification of total LC3 on actin is reported (*P = 0.01248). The results are representative of three independent experiments.Representative images of p62 dots in KO+KRIT1 (top) and KRIT1-KO cells (bottom). Scale bar, 50 μm. Magnifications in insets. Right, quantitative analysis of the number of p62 dots per cell is shown (four independent experiments; n = 50 cells per group). *P = 7.18e−14.Immunoblot analysis of hBMECs transiently transfected with control siRNA or KRIT1 siRNA. Left, evaluation of siRNA efficiency with antibody directed against KRIT1. Right, immunoblots for p62 and LC3 I/II. Actin was used as a loading marker. Quantification of total LC3 on actin is reported (*P = 0.03071). The results are representative of three independent experiments.Immunoblot analysis of EA.hy926 cells transiently transfected with control siRNA or KRIT1 siRNA. Left, evaluation of siRNA efficiency with antibody directed against KRIT1. Right, immunoblot for p62 and LC3 I/II. Actin was used as a loading marker. Quantification of total LC3 on actin is reported (*P = 0.02527). The results are representative of three independent experiments.Immunofluorescence analysis of p62 (green) and ProteoStat Aggresome staining detection reagent (red) in KRIT1 wt and KRIT1-KO lung endothelial cells. The yellow signal in the merged images represents an overlapping spatial relationship between green and red fluorescence. Magnification in insets. Scale bar, 50 μm. The images are representative of four independent experiments.Immunofluorescence analysis of p62 (green) and ProteoStat Aggresome staining detection reagent (red) in KRIT1-KO re-expressing KRIT1 (KO+KRIT1) and KRIT1-KO MEFs. The yellow signal in the merged images represents an overlapping spatial relationship between green and red fluorescence. Magnification in insets. Scale bar, 50 μm. The images are representative of four independent experiments.Source data are available online for this figure.

Mentions: p62/SQSTM1 acts as a receptor for ubiquitinated cargoes and delivers them to the autophagosome, and p62 itself is incorporated into the autophagosome and subsequently degraded by autophagy (Komatsu et al, 2007). The autophagy protein microtubule-associated protein 1 light chain 3 (LC3) is present in the cytosol in the LC3-I form, until it is modified to a cleaved and lipidated membrane-bound form (LC3-II), which is localized to autophagosomes. Thus, in addition to p62 accumulation, another typical trait of autophagy inhibition consists of increased amounts of the cytosolic non-lipidated form of LC3 (LC3-I) and of total LC3 (Mizushima et al, 2010; Wang et al, 2012). As shown in Fig1A, KRIT1 deficiency was associated with defective autophagy, displaying increased levels of p62 and total LC3.


Defective autophagy is a key feature of cerebral cavernous malformations.

Marchi S, Corricelli M, Trapani E, Bravi L, Pittaro A, Delle Monache S, Ferroni L, Patergnani S, Missiroli S, Goitre L, Trabalzini L, Rimessi A, Giorgi C, Zavan B, Cassoni P, Dejana E, Retta SF, Pinton P - EMBO Mol Med (2015)

KRIT1-ablated cells display autophagy suppressionImmunoblot analysis of p62 and LC3 I/II in KRIT1 wt and KRIT1-KO endothelial cells. Actin was used as a loading control. Quantification of total LC3 on actin is reported (*P = 0.02712). The results are representative of three independent experiments.Representative images of p62 dots in KRIT1 wt and KRIT1-KO endothelial cells. Scale bar, 20 μm. Magnifications in insets. Right, quantitative analysis of p62 distribution of dots is reported (four independent experiments; n = 35 cells per group). *P = 0.00542 (dotted); *P = 0.00014 (nuclear).Immunoblot analysis of p62 and LC3 I/II in KRIT1-KO and KRIT1-KO re-expressing KRIT1 (KO+KRIT1) MEFs. Left, immunoblot showing KRIT1 levels in KRIT1-KO and KO+KRIT1 cells. Right, immunoblots for p62 and LC3 I/II. Actin was used as a loading marker. Quantification of total LC3 on actin is reported (*P = 0.01248). The results are representative of three independent experiments.Representative images of p62 dots in KO+KRIT1 (top) and KRIT1-KO cells (bottom). Scale bar, 50 μm. Magnifications in insets. Right, quantitative analysis of the number of p62 dots per cell is shown (four independent experiments; n = 50 cells per group). *P = 7.18e−14.Immunoblot analysis of hBMECs transiently transfected with control siRNA or KRIT1 siRNA. Left, evaluation of siRNA efficiency with antibody directed against KRIT1. Right, immunoblots for p62 and LC3 I/II. Actin was used as a loading marker. Quantification of total LC3 on actin is reported (*P = 0.03071). The results are representative of three independent experiments.Immunoblot analysis of EA.hy926 cells transiently transfected with control siRNA or KRIT1 siRNA. Left, evaluation of siRNA efficiency with antibody directed against KRIT1. Right, immunoblot for p62 and LC3 I/II. Actin was used as a loading marker. Quantification of total LC3 on actin is reported (*P = 0.02527). The results are representative of three independent experiments.Immunofluorescence analysis of p62 (green) and ProteoStat Aggresome staining detection reagent (red) in KRIT1 wt and KRIT1-KO lung endothelial cells. The yellow signal in the merged images represents an overlapping spatial relationship between green and red fluorescence. Magnification in insets. Scale bar, 50 μm. The images are representative of four independent experiments.Immunofluorescence analysis of p62 (green) and ProteoStat Aggresome staining detection reagent (red) in KRIT1-KO re-expressing KRIT1 (KO+KRIT1) and KRIT1-KO MEFs. The yellow signal in the merged images represents an overlapping spatial relationship between green and red fluorescence. Magnification in insets. Scale bar, 50 μm. The images are representative of four independent experiments.Source data are available online for this figure.
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fig01: KRIT1-ablated cells display autophagy suppressionImmunoblot analysis of p62 and LC3 I/II in KRIT1 wt and KRIT1-KO endothelial cells. Actin was used as a loading control. Quantification of total LC3 on actin is reported (*P = 0.02712). The results are representative of three independent experiments.Representative images of p62 dots in KRIT1 wt and KRIT1-KO endothelial cells. Scale bar, 20 μm. Magnifications in insets. Right, quantitative analysis of p62 distribution of dots is reported (four independent experiments; n = 35 cells per group). *P = 0.00542 (dotted); *P = 0.00014 (nuclear).Immunoblot analysis of p62 and LC3 I/II in KRIT1-KO and KRIT1-KO re-expressing KRIT1 (KO+KRIT1) MEFs. Left, immunoblot showing KRIT1 levels in KRIT1-KO and KO+KRIT1 cells. Right, immunoblots for p62 and LC3 I/II. Actin was used as a loading marker. Quantification of total LC3 on actin is reported (*P = 0.01248). The results are representative of three independent experiments.Representative images of p62 dots in KO+KRIT1 (top) and KRIT1-KO cells (bottom). Scale bar, 50 μm. Magnifications in insets. Right, quantitative analysis of the number of p62 dots per cell is shown (four independent experiments; n = 50 cells per group). *P = 7.18e−14.Immunoblot analysis of hBMECs transiently transfected with control siRNA or KRIT1 siRNA. Left, evaluation of siRNA efficiency with antibody directed against KRIT1. Right, immunoblots for p62 and LC3 I/II. Actin was used as a loading marker. Quantification of total LC3 on actin is reported (*P = 0.03071). The results are representative of three independent experiments.Immunoblot analysis of EA.hy926 cells transiently transfected with control siRNA or KRIT1 siRNA. Left, evaluation of siRNA efficiency with antibody directed against KRIT1. Right, immunoblot for p62 and LC3 I/II. Actin was used as a loading marker. Quantification of total LC3 on actin is reported (*P = 0.02527). The results are representative of three independent experiments.Immunofluorescence analysis of p62 (green) and ProteoStat Aggresome staining detection reagent (red) in KRIT1 wt and KRIT1-KO lung endothelial cells. The yellow signal in the merged images represents an overlapping spatial relationship between green and red fluorescence. Magnification in insets. Scale bar, 50 μm. The images are representative of four independent experiments.Immunofluorescence analysis of p62 (green) and ProteoStat Aggresome staining detection reagent (red) in KRIT1-KO re-expressing KRIT1 (KO+KRIT1) and KRIT1-KO MEFs. The yellow signal in the merged images represents an overlapping spatial relationship between green and red fluorescence. Magnification in insets. Scale bar, 50 μm. The images are representative of four independent experiments.Source data are available online for this figure.
Mentions: p62/SQSTM1 acts as a receptor for ubiquitinated cargoes and delivers them to the autophagosome, and p62 itself is incorporated into the autophagosome and subsequently degraded by autophagy (Komatsu et al, 2007). The autophagy protein microtubule-associated protein 1 light chain 3 (LC3) is present in the cytosol in the LC3-I form, until it is modified to a cleaved and lipidated membrane-bound form (LC3-II), which is localized to autophagosomes. Thus, in addition to p62 accumulation, another typical trait of autophagy inhibition consists of increased amounts of the cytosolic non-lipidated form of LC3 (LC3-I) and of total LC3 (Mizushima et al, 2010; Wang et al, 2012). As shown in Fig1A, KRIT1 deficiency was associated with defective autophagy, displaying increased levels of p62 and total LC3.

Bottom Line: KRIT1 loss-of-function activates the mTOR-ULK1 pathway, which is a master regulator of autophagy, and treatment with mTOR inhibitors rescues some of the mole-cular and cellular phenotypes associated with CCM.Furthermore, defective autophagy is highly correlated to endothelial-to-mesenchymal transition, a crucial event that contributes to CCM progression.Taken together, our data point to a key role for defective autophagy in CCM disease pathogenesis, thus providing a novel framework for the development of new pharmacological strategies to prevent or reverse adverse clinical outcomes of CCM lesions.

View Article: PubMed Central - PubMed

Affiliation: Department of Morphology, Surgery and Experimental Medicine, Section of Pathology Oncology and Experimental Biology, University of Ferrara, Ferrara, Italy.

Show MeSH
Related in: MedlinePlus