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Plasma membrane overgrowth causes fibrotic collagen accumulation and immune activation in Drosophila adipocytes.

Zang Y, Wan M, Liu M, Ke H, Ma S, Liu LP, Ni JQ, Pastor-Pareja JC - Elife (2015)

Bottom Line: Deposits also form in the absence of negative Toll immune regulator Cactus, excess PM being caused in this case by increased secretion.Finally, we show that trimeric Collagen accumulation, downstream of Toll or endocytic defects, activates a tissue damage response.It also places fibrotic deposits both downstream and upstream of immune signaling, consistent with the chronic character of fibrotic diseases.

View Article: PubMed Central - PubMed

Affiliation: School of Life Sciences, Tsinghua University, Beijing, China.

ABSTRACT
Many chronic diseases are associated with fibrotic deposition of Collagen and other matrix proteins. Little is known about the factors that determine preferential onset of fibrosis in particular tissues. Here we show that plasma membrane (PM) overgrowth causes pericellular Collagen accumulation in Drosophila adipocytes. We found that loss of Dynamin and other endocytic components causes pericellular trapping of outgoing Collagen IV due to dramatic cortex expansion when endocytic removal of PM is prevented. Deposits also form in the absence of negative Toll immune regulator Cactus, excess PM being caused in this case by increased secretion. Finally, we show that trimeric Collagen accumulation, downstream of Toll or endocytic defects, activates a tissue damage response. Our work indicates that traffic imbalances and PM topology may contribute to fibrosis. It also places fibrotic deposits both downstream and upstream of immune signaling, consistent with the chronic character of fibrotic diseases.

No MeSH data available.


Related in: MedlinePlus

(A) Nuclear accumulation of the Toll downstream transcription factor Dorsal (anti-Dorsal staining) in BM-40-SPARC>cacti adipocytes.(B) Pericellular Cg25C accumulation in adipocytes of mutant cact4 over cact-uncovering deficiency Df(2L)r10. (C) Electron micrographs of the PM of BM-40-SPARC>cacti and >Tl10B adipocytes. Asterisks mark pericellular deposits. Arrows mark visible connections of the deposits to the extracellular space. (D) Antibody stainings of cacti and Tl10B adipocytes performed without permeabilization (no detergent) in order to detect extracellular Collagen IV. (E) Knock-down of Dif decreases the expression of Toll target gene Drosomycin (Drs-GFP) activated by cacti and Tl10B (BM-40-SPARC>cacti and >Tl10B adipocytes). (F) Localization of endocytic marker TfR-GFP in wild type, Cg>shii and Cg>cacti adipocytes. Intracellular TfR vesicles are seen in cacti adipocytes, same as wild type. (G) Drosomycin-containing vesicles (Drs-GFP) in the cytoplasm of BM-40-SPARC>Tl10B adipocytes. (H) Pericellular retention of Collagen IV (Vkg-GFP) at the PM of adipocytes from larvae dissected 1 or 2 days after Micrococcus luteus infection.DOI:http://dx.doi.org/10.7554/eLife.07187.015
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fig6s1: (A) Nuclear accumulation of the Toll downstream transcription factor Dorsal (anti-Dorsal staining) in BM-40-SPARC>cacti adipocytes.(B) Pericellular Cg25C accumulation in adipocytes of mutant cact4 over cact-uncovering deficiency Df(2L)r10. (C) Electron micrographs of the PM of BM-40-SPARC>cacti and >Tl10B adipocytes. Asterisks mark pericellular deposits. Arrows mark visible connections of the deposits to the extracellular space. (D) Antibody stainings of cacti and Tl10B adipocytes performed without permeabilization (no detergent) in order to detect extracellular Collagen IV. (E) Knock-down of Dif decreases the expression of Toll target gene Drosomycin (Drs-GFP) activated by cacti and Tl10B (BM-40-SPARC>cacti and >Tl10B adipocytes). (F) Localization of endocytic marker TfR-GFP in wild type, Cg>shii and Cg>cacti adipocytes. Intracellular TfR vesicles are seen in cacti adipocytes, same as wild type. (G) Drosomycin-containing vesicles (Drs-GFP) in the cytoplasm of BM-40-SPARC>Tl10B adipocytes. (H) Pericellular retention of Collagen IV (Vkg-GFP) at the PM of adipocytes from larvae dissected 1 or 2 days after Micrococcus luteus infection.DOI:http://dx.doi.org/10.7554/eLife.07187.015

Mentions: Having established that extracellular deposits caused by PM overgrowth were not general protein aggregates but rather fibrotic ECM aggregates, we decided to investigate their wider biological effects. To do that, we first turned our attention to cactus, another PM accumulation hit in our screening (Figure 6A). cactus (cact) encodes a negative regulator of the Toll signaling pathway, a key mediator of innate immunity (Roth et al., 1991). We confirmed activation of Toll signaling in cacti adipocytes (Dorsal nuclear accumulation) and further validated the phenotype by observing pericellular Collagen accumulation in cact4 mutants (Roth et al., 1991) (Figure 6—figure supplement 1). Expression of the constitutively active mutant receptor Toll10B also produced pericellular Collagen accumulation (Figure 6B), as did infection with Toll-activating Gram+ bacteria Micrococcus luteus (Figure 6C; Figure 6—figure supplement 1). Examination of cacti and Toll10B adipocytes in confocal and electron micrographs revealed PM overgrowth (Figure 6D,E), similar to shii adipocytes. Also similar to shii adipocytes, PM overgrowth upon Toll activation was suppressed by lipid-depleted food (graph in Figure 6E). Moreover, pericellular Collagen IV deposits were extracellular (antibody staining without permeabilization, Figure 6—figure supplement 1), disappeared upon PH4αEFB knock-down (Figure 6F) and did not contain secr-GFP (Figure 6G), but contained Perlecan (Figure 6H), indicating accumulation of fibrotic material, same as in endocytosis-defective cells.10.7554/eLife.07187.014Figure 6.Fibrotic deposits and PM overgrowth upon Toll activation.


Plasma membrane overgrowth causes fibrotic collagen accumulation and immune activation in Drosophila adipocytes.

Zang Y, Wan M, Liu M, Ke H, Ma S, Liu LP, Ni JQ, Pastor-Pareja JC - Elife (2015)

(A) Nuclear accumulation of the Toll downstream transcription factor Dorsal (anti-Dorsal staining) in BM-40-SPARC>cacti adipocytes.(B) Pericellular Cg25C accumulation in adipocytes of mutant cact4 over cact-uncovering deficiency Df(2L)r10. (C) Electron micrographs of the PM of BM-40-SPARC>cacti and >Tl10B adipocytes. Asterisks mark pericellular deposits. Arrows mark visible connections of the deposits to the extracellular space. (D) Antibody stainings of cacti and Tl10B adipocytes performed without permeabilization (no detergent) in order to detect extracellular Collagen IV. (E) Knock-down of Dif decreases the expression of Toll target gene Drosomycin (Drs-GFP) activated by cacti and Tl10B (BM-40-SPARC>cacti and >Tl10B adipocytes). (F) Localization of endocytic marker TfR-GFP in wild type, Cg>shii and Cg>cacti adipocytes. Intracellular TfR vesicles are seen in cacti adipocytes, same as wild type. (G) Drosomycin-containing vesicles (Drs-GFP) in the cytoplasm of BM-40-SPARC>Tl10B adipocytes. (H) Pericellular retention of Collagen IV (Vkg-GFP) at the PM of adipocytes from larvae dissected 1 or 2 days after Micrococcus luteus infection.DOI:http://dx.doi.org/10.7554/eLife.07187.015
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Related In: Results  -  Collection

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fig6s1: (A) Nuclear accumulation of the Toll downstream transcription factor Dorsal (anti-Dorsal staining) in BM-40-SPARC>cacti adipocytes.(B) Pericellular Cg25C accumulation in adipocytes of mutant cact4 over cact-uncovering deficiency Df(2L)r10. (C) Electron micrographs of the PM of BM-40-SPARC>cacti and >Tl10B adipocytes. Asterisks mark pericellular deposits. Arrows mark visible connections of the deposits to the extracellular space. (D) Antibody stainings of cacti and Tl10B adipocytes performed without permeabilization (no detergent) in order to detect extracellular Collagen IV. (E) Knock-down of Dif decreases the expression of Toll target gene Drosomycin (Drs-GFP) activated by cacti and Tl10B (BM-40-SPARC>cacti and >Tl10B adipocytes). (F) Localization of endocytic marker TfR-GFP in wild type, Cg>shii and Cg>cacti adipocytes. Intracellular TfR vesicles are seen in cacti adipocytes, same as wild type. (G) Drosomycin-containing vesicles (Drs-GFP) in the cytoplasm of BM-40-SPARC>Tl10B adipocytes. (H) Pericellular retention of Collagen IV (Vkg-GFP) at the PM of adipocytes from larvae dissected 1 or 2 days after Micrococcus luteus infection.DOI:http://dx.doi.org/10.7554/eLife.07187.015
Mentions: Having established that extracellular deposits caused by PM overgrowth were not general protein aggregates but rather fibrotic ECM aggregates, we decided to investigate their wider biological effects. To do that, we first turned our attention to cactus, another PM accumulation hit in our screening (Figure 6A). cactus (cact) encodes a negative regulator of the Toll signaling pathway, a key mediator of innate immunity (Roth et al., 1991). We confirmed activation of Toll signaling in cacti adipocytes (Dorsal nuclear accumulation) and further validated the phenotype by observing pericellular Collagen accumulation in cact4 mutants (Roth et al., 1991) (Figure 6—figure supplement 1). Expression of the constitutively active mutant receptor Toll10B also produced pericellular Collagen accumulation (Figure 6B), as did infection with Toll-activating Gram+ bacteria Micrococcus luteus (Figure 6C; Figure 6—figure supplement 1). Examination of cacti and Toll10B adipocytes in confocal and electron micrographs revealed PM overgrowth (Figure 6D,E), similar to shii adipocytes. Also similar to shii adipocytes, PM overgrowth upon Toll activation was suppressed by lipid-depleted food (graph in Figure 6E). Moreover, pericellular Collagen IV deposits were extracellular (antibody staining without permeabilization, Figure 6—figure supplement 1), disappeared upon PH4αEFB knock-down (Figure 6F) and did not contain secr-GFP (Figure 6G), but contained Perlecan (Figure 6H), indicating accumulation of fibrotic material, same as in endocytosis-defective cells.10.7554/eLife.07187.014Figure 6.Fibrotic deposits and PM overgrowth upon Toll activation.

Bottom Line: Deposits also form in the absence of negative Toll immune regulator Cactus, excess PM being caused in this case by increased secretion.Finally, we show that trimeric Collagen accumulation, downstream of Toll or endocytic defects, activates a tissue damage response.It also places fibrotic deposits both downstream and upstream of immune signaling, consistent with the chronic character of fibrotic diseases.

View Article: PubMed Central - PubMed

Affiliation: School of Life Sciences, Tsinghua University, Beijing, China.

ABSTRACT
Many chronic diseases are associated with fibrotic deposition of Collagen and other matrix proteins. Little is known about the factors that determine preferential onset of fibrosis in particular tissues. Here we show that plasma membrane (PM) overgrowth causes pericellular Collagen accumulation in Drosophila adipocytes. We found that loss of Dynamin and other endocytic components causes pericellular trapping of outgoing Collagen IV due to dramatic cortex expansion when endocytic removal of PM is prevented. Deposits also form in the absence of negative Toll immune regulator Cactus, excess PM being caused in this case by increased secretion. Finally, we show that trimeric Collagen accumulation, downstream of Toll or endocytic defects, activates a tissue damage response. Our work indicates that traffic imbalances and PM topology may contribute to fibrosis. It also places fibrotic deposits both downstream and upstream of immune signaling, consistent with the chronic character of fibrotic diseases.

No MeSH data available.


Related in: MedlinePlus