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Lazarillo-related Lipocalins confer long-term protection against type I Spinocerebellar Ataxia degeneration contributing to optimize selective autophagy.

del Caño-Espinel M, Acebes JR, Sanchez D, Ganfornina MD - Mol Neurodegener (2015)

Bottom Line: GLaz beneficial effects persist throughout aging, and appears when expressed by degenerating neurons or by retinal support and glial cells.GLaz gain-of-function reduces cell death and the extent of ubiquitinated proteins accumulation, and decreases the expression of Atg8a/LC3, p62 mRNA and protein levels, and GstS1 induction.Down-regulation of selective autophagy causes similar and non-additive rescuing effects.

View Article: PubMed Central - PubMed

Affiliation: Instituto de Biología y Genética Molecular-Departamento de Bioquímica y Biología Molecular y Fisiología, Universidad de Valladolid-CSIC, c/ Sanz y Forés 3, 47003, Valladolid, Spain. manuela@ibgm.uva.es.

ABSTRACT

Background: A diverse set of neurodegenerative disorders are caused by abnormal extensions of polyglutamine (poly-Q) stretches in various, functionally unrelated proteins. A common feature of these diseases is altered proteostasis. Autophagy induction is part of the endogenous response to poly-Q protein expression. However, if autophagy is not resolved properly, clearance of toxic proteins or aggregates cannot occur effectively. Likewise, excessive autophagy induction can cause autophagic stress and neurodegeneration. The Lipocalins ApoD, Glial Lazarillo (GLaz) and Neural Lazarillo (NLaz) are neuroprotectors upon oxidative stress or aging. In this work we test whether these Lipocalins also protect against poly-Q-triggered deterioration of protein quality control systems.

Results: Using a Drosophila retinal degeneration model of Type-1 Spinocerebellar Ataxia (SCA1) combined with genetic manipulation of NLaz and GLaz expression, we demonstrate that both Lipocalins protect against SCA1 neurodegeneration. They are part of the endogenous transcriptional response to SCA1, and their effect is non-additive, suggesting participation in a similar mechanism. GLaz beneficial effects persist throughout aging, and appears when expressed by degenerating neurons or by retinal support and glial cells. GLaz gain-of-function reduces cell death and the extent of ubiquitinated proteins accumulation, and decreases the expression of Atg8a/LC3, p62 mRNA and protein levels, and GstS1 induction. Over-expression of GLaz is able to reduce p62 and ubiquitinated proteins levels when rapamycin-dependent and SCA1-dependent inductions of autophagy are combined. In the absence of neurodegeneration, GLaz loss-of-function increases Atg8a/LC3 mRNA and p62 protein levels without altering p62 mRNA levels. Knocking-down autophagy, by interfering with Atg8a or p62 expression or by expressing dominant-negative Atg1/ULK1 or Atg4a transgenes, rescues SCA1-dependent neurodegeneration in a similar extent to the protective effect of GLaz. Further GLaz-dependent improvement is concealed.

Conclusions: This work shows for the first time that a Lipocalin rescues neurons from pathogenic SCA1 degeneration by optimizing clearance of aggregation-prone proteins. GLaz modulates key autophagy genes and lipid-peroxide clearance responsive genes. Down-regulation of selective autophagy causes similar and non-additive rescuing effects. These data suggest that SCA1 neurodegeneration concurs with autophagic stress, and places Lazarillo-related Lipocalins as valuable players in the endogenous protection against the two major contributors to aging and neurodegeneration: ROS-dependent damage and proteostasis deterioration.

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Epistasis analysis of GLaz with down-regulators of autophagy. A, Quantitative estimate of degeneration by computing a regularity index based on the variance (σ) of the local intensity maxima distances. A percent recovery of the degeneration is indicated for each genotype. 20–35 eyes/genotype were used to compute regularity indexes. Average ± S.E.M. are represented. Asterisk represents statistically significant differences (Student’s t-test, *P < 0.05) with respect to the degenerated gmr > hATXN182Q genotype. B-E, Adult (3d old) Drosophila eye morphology of gmr > hATXN182Q + autophagy down-regulators, compared to gmr > hATXN182Q + GLaz2 + autophagy down-regulators. Representative examples of light microscopy and surface filter-processed image of the central retinal region are shown.
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Fig9: Epistasis analysis of GLaz with down-regulators of autophagy. A, Quantitative estimate of degeneration by computing a regularity index based on the variance (σ) of the local intensity maxima distances. A percent recovery of the degeneration is indicated for each genotype. 20–35 eyes/genotype were used to compute regularity indexes. Average ± S.E.M. are represented. Asterisk represents statistically significant differences (Student’s t-test, *P < 0.05) with respect to the degenerated gmr > hATXN182Q genotype. B-E, Adult (3d old) Drosophila eye morphology of gmr > hATXN182Q + autophagy down-regulators, compared to gmr > hATXN182Q + GLaz2 + autophagy down-regulators. Representative examples of light microscopy and surface filter-processed image of the central retinal region are shown.

Mentions: We used four genetic manipulations to decrease autophagy activity in our SCA1 Drosophila model: Atg1K38Q, a kinase-negative form of Atg1 that inhibits starvation- and rapamycin-induced autophagy [46] by impairing the induction of autophagosome formation; Atg4aC98A, a dominant-negative form of Atg4a suppressing autophagy by defective processing of Atg8a/LC3 [47]; RNAi silencing of Atg8a (JF02895 line) [Dr. Juhász personal communication] and of p62 (KK105338 line) [47], that reduce Atg8a or p62 up-regulation respectively and impair the replenishment of both proteins when they are consumed by autophagic activity. The four constructs were expressed with the UAS/GAL4 system in the neurodegenerating photoreceptors with or without over-expression of GLaz (Figure 9).Figure 9


Lazarillo-related Lipocalins confer long-term protection against type I Spinocerebellar Ataxia degeneration contributing to optimize selective autophagy.

del Caño-Espinel M, Acebes JR, Sanchez D, Ganfornina MD - Mol Neurodegener (2015)

Epistasis analysis of GLaz with down-regulators of autophagy. A, Quantitative estimate of degeneration by computing a regularity index based on the variance (σ) of the local intensity maxima distances. A percent recovery of the degeneration is indicated for each genotype. 20–35 eyes/genotype were used to compute regularity indexes. Average ± S.E.M. are represented. Asterisk represents statistically significant differences (Student’s t-test, *P < 0.05) with respect to the degenerated gmr > hATXN182Q genotype. B-E, Adult (3d old) Drosophila eye morphology of gmr > hATXN182Q + autophagy down-regulators, compared to gmr > hATXN182Q + GLaz2 + autophagy down-regulators. Representative examples of light microscopy and surface filter-processed image of the central retinal region are shown.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4374295&req=5

Fig9: Epistasis analysis of GLaz with down-regulators of autophagy. A, Quantitative estimate of degeneration by computing a regularity index based on the variance (σ) of the local intensity maxima distances. A percent recovery of the degeneration is indicated for each genotype. 20–35 eyes/genotype were used to compute regularity indexes. Average ± S.E.M. are represented. Asterisk represents statistically significant differences (Student’s t-test, *P < 0.05) with respect to the degenerated gmr > hATXN182Q genotype. B-E, Adult (3d old) Drosophila eye morphology of gmr > hATXN182Q + autophagy down-regulators, compared to gmr > hATXN182Q + GLaz2 + autophagy down-regulators. Representative examples of light microscopy and surface filter-processed image of the central retinal region are shown.
Mentions: We used four genetic manipulations to decrease autophagy activity in our SCA1 Drosophila model: Atg1K38Q, a kinase-negative form of Atg1 that inhibits starvation- and rapamycin-induced autophagy [46] by impairing the induction of autophagosome formation; Atg4aC98A, a dominant-negative form of Atg4a suppressing autophagy by defective processing of Atg8a/LC3 [47]; RNAi silencing of Atg8a (JF02895 line) [Dr. Juhász personal communication] and of p62 (KK105338 line) [47], that reduce Atg8a or p62 up-regulation respectively and impair the replenishment of both proteins when they are consumed by autophagic activity. The four constructs were expressed with the UAS/GAL4 system in the neurodegenerating photoreceptors with or without over-expression of GLaz (Figure 9).Figure 9

Bottom Line: GLaz beneficial effects persist throughout aging, and appears when expressed by degenerating neurons or by retinal support and glial cells.GLaz gain-of-function reduces cell death and the extent of ubiquitinated proteins accumulation, and decreases the expression of Atg8a/LC3, p62 mRNA and protein levels, and GstS1 induction.Down-regulation of selective autophagy causes similar and non-additive rescuing effects.

View Article: PubMed Central - PubMed

Affiliation: Instituto de Biología y Genética Molecular-Departamento de Bioquímica y Biología Molecular y Fisiología, Universidad de Valladolid-CSIC, c/ Sanz y Forés 3, 47003, Valladolid, Spain. manuela@ibgm.uva.es.

ABSTRACT

Background: A diverse set of neurodegenerative disorders are caused by abnormal extensions of polyglutamine (poly-Q) stretches in various, functionally unrelated proteins. A common feature of these diseases is altered proteostasis. Autophagy induction is part of the endogenous response to poly-Q protein expression. However, if autophagy is not resolved properly, clearance of toxic proteins or aggregates cannot occur effectively. Likewise, excessive autophagy induction can cause autophagic stress and neurodegeneration. The Lipocalins ApoD, Glial Lazarillo (GLaz) and Neural Lazarillo (NLaz) are neuroprotectors upon oxidative stress or aging. In this work we test whether these Lipocalins also protect against poly-Q-triggered deterioration of protein quality control systems.

Results: Using a Drosophila retinal degeneration model of Type-1 Spinocerebellar Ataxia (SCA1) combined with genetic manipulation of NLaz and GLaz expression, we demonstrate that both Lipocalins protect against SCA1 neurodegeneration. They are part of the endogenous transcriptional response to SCA1, and their effect is non-additive, suggesting participation in a similar mechanism. GLaz beneficial effects persist throughout aging, and appears when expressed by degenerating neurons or by retinal support and glial cells. GLaz gain-of-function reduces cell death and the extent of ubiquitinated proteins accumulation, and decreases the expression of Atg8a/LC3, p62 mRNA and protein levels, and GstS1 induction. Over-expression of GLaz is able to reduce p62 and ubiquitinated proteins levels when rapamycin-dependent and SCA1-dependent inductions of autophagy are combined. In the absence of neurodegeneration, GLaz loss-of-function increases Atg8a/LC3 mRNA and p62 protein levels without altering p62 mRNA levels. Knocking-down autophagy, by interfering with Atg8a or p62 expression or by expressing dominant-negative Atg1/ULK1 or Atg4a transgenes, rescues SCA1-dependent neurodegeneration in a similar extent to the protective effect of GLaz. Further GLaz-dependent improvement is concealed.

Conclusions: This work shows for the first time that a Lipocalin rescues neurons from pathogenic SCA1 degeneration by optimizing clearance of aggregation-prone proteins. GLaz modulates key autophagy genes and lipid-peroxide clearance responsive genes. Down-regulation of selective autophagy causes similar and non-additive rescuing effects. These data suggest that SCA1 neurodegeneration concurs with autophagic stress, and places Lazarillo-related Lipocalins as valuable players in the endogenous protection against the two major contributors to aging and neurodegeneration: ROS-dependent damage and proteostasis deterioration.

Show MeSH
Related in: MedlinePlus