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Endosome – mitochondria interactions are modulated by iron release from transferrin

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ABSTRACT

Using superresolution and quantitative fluorescence microscopy, Das et al. have revealed that iron-transferrin–containing endosomes directly interact with mitochondria, facilitating iron transfer in epithelial cells. Their findings further enrich the repertoire of organelle–organelle direct interactions to accomplish a functional significance.

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Related in: MedlinePlus

Tf-endosomal motility is reduced upon interaction with mitochondria. MitoTracker orange–labeled MDCK-PTR cells were pulsed with AF488-hTf for 2 min at 37°C and chased, and time-lapse images of 15-s duration (139-ms interval) were acquired at 5 min after the hTf pulse. (A) Double-labeled fluorescence image from a representative time lapse (a); corresponding 3D render where AF488 hTf-endosomes are green spots and mitochondria are red surfaces (b); 3D-rendered image subjected to a DT 0–based kiss and run filter selecting only those Tf-endosomes that are in close proximity to mitochondria (c; see Video 5); magnified ROI (d; white box in c); magnified ROI (white box in d) where the selected hTf-endosome (yellow spot) is in close proximity to a mitochondrion (e). Bars: (a–d) 10.0 µm; (e) 1.0 µm. (B) Videomicrograph (top row, fluorescence; bottom row, 3D rendered) of the kiss and run interaction between the selected hTf-endosome and mitochondrion (A e) proceeds from left to right at a 139-ms frame interval. Graph represents the hTf-endosomal instantaneous speed (blue line) with respect to its corresponding DT-based distance from the mitochondrion (red line) over time. Dashed box in videomicrograph and graph indicates the kiss phase. hTf-endosomal instantaneous speed is markedly reduced when it is in close proximity to the mitochondrion, denoted by the overlapping of the red line with the x axis. See Videos 6 and 7, which show two additional hTf-endosomal kiss and run events. Bar, 0.5 µm.
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fig4: Tf-endosomal motility is reduced upon interaction with mitochondria. MitoTracker orange–labeled MDCK-PTR cells were pulsed with AF488-hTf for 2 min at 37°C and chased, and time-lapse images of 15-s duration (139-ms interval) were acquired at 5 min after the hTf pulse. (A) Double-labeled fluorescence image from a representative time lapse (a); corresponding 3D render where AF488 hTf-endosomes are green spots and mitochondria are red surfaces (b); 3D-rendered image subjected to a DT 0–based kiss and run filter selecting only those Tf-endosomes that are in close proximity to mitochondria (c; see Video 5); magnified ROI (d; white box in c); magnified ROI (white box in d) where the selected hTf-endosome (yellow spot) is in close proximity to a mitochondrion (e). Bars: (a–d) 10.0 µm; (e) 1.0 µm. (B) Videomicrograph (top row, fluorescence; bottom row, 3D rendered) of the kiss and run interaction between the selected hTf-endosome and mitochondrion (A e) proceeds from left to right at a 139-ms frame interval. Graph represents the hTf-endosomal instantaneous speed (blue line) with respect to its corresponding DT-based distance from the mitochondrion (red line) over time. Dashed box in videomicrograph and graph indicates the kiss phase. hTf-endosomal instantaneous speed is markedly reduced when it is in close proximity to the mitochondrion, denoted by the overlapping of the red line with the x axis. See Videos 6 and 7, which show two additional hTf-endosomal kiss and run events. Bar, 0.5 µm.

Mentions: To investigate the prevalence of endosome–mitochondria interactions within the early endocytic pathway, we established a criterion to quantitatively measure interactions in an unbiased and semiautomated manner. Previously, quantitative analyses of cell-to-cell (Malide et al., 2012; McKee et al., 2013) or organelle–organelle interactions (Whalen et al., 2012; Bouvet et al., 2013; Wang et al., 2015) were performed using the distance transformation (DT) algorithm. DT is a representation of the digital image in terms of pixels with assigned values based on their respective distances from the boundary of a specific object. Therefore, 3D rendering of the object in question is a prerequisite for carrying out the DT operation. Here, we used the DT algorithm, built in the image analysis software Imaris, for quantitative determination of the distance of Tf-endosomes from the boundary of 3D-rendered mitochondrial surfaces, which are considered to be the anchor organelle, as they are less dynamic than endosomes. The DT criterion was evaluated for its consistency and reliability on immunofluorescent fixed cells (Fig. 2) before it was used in the analysis of time-lapse videos to study the dynamics of endosome–mitochondria interactions in live cells (see Figs. 3, 4, and 5).


Endosome – mitochondria interactions are modulated by iron release from transferrin
Tf-endosomal motility is reduced upon interaction with mitochondria. MitoTracker orange–labeled MDCK-PTR cells were pulsed with AF488-hTf for 2 min at 37°C and chased, and time-lapse images of 15-s duration (139-ms interval) were acquired at 5 min after the hTf pulse. (A) Double-labeled fluorescence image from a representative time lapse (a); corresponding 3D render where AF488 hTf-endosomes are green spots and mitochondria are red surfaces (b); 3D-rendered image subjected to a DT 0–based kiss and run filter selecting only those Tf-endosomes that are in close proximity to mitochondria (c; see Video 5); magnified ROI (d; white box in c); magnified ROI (white box in d) where the selected hTf-endosome (yellow spot) is in close proximity to a mitochondrion (e). Bars: (a–d) 10.0 µm; (e) 1.0 µm. (B) Videomicrograph (top row, fluorescence; bottom row, 3D rendered) of the kiss and run interaction between the selected hTf-endosome and mitochondrion (A e) proceeds from left to right at a 139-ms frame interval. Graph represents the hTf-endosomal instantaneous speed (blue line) with respect to its corresponding DT-based distance from the mitochondrion (red line) over time. Dashed box in videomicrograph and graph indicates the kiss phase. hTf-endosomal instantaneous speed is markedly reduced when it is in close proximity to the mitochondrion, denoted by the overlapping of the red line with the x axis. See Videos 6 and 7, which show two additional hTf-endosomal kiss and run events. Bar, 0.5 µm.
© Copyright Policy - openaccess
Related In: Results  -  Collection

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fig4: Tf-endosomal motility is reduced upon interaction with mitochondria. MitoTracker orange–labeled MDCK-PTR cells were pulsed with AF488-hTf for 2 min at 37°C and chased, and time-lapse images of 15-s duration (139-ms interval) were acquired at 5 min after the hTf pulse. (A) Double-labeled fluorescence image from a representative time lapse (a); corresponding 3D render where AF488 hTf-endosomes are green spots and mitochondria are red surfaces (b); 3D-rendered image subjected to a DT 0–based kiss and run filter selecting only those Tf-endosomes that are in close proximity to mitochondria (c; see Video 5); magnified ROI (d; white box in c); magnified ROI (white box in d) where the selected hTf-endosome (yellow spot) is in close proximity to a mitochondrion (e). Bars: (a–d) 10.0 µm; (e) 1.0 µm. (B) Videomicrograph (top row, fluorescence; bottom row, 3D rendered) of the kiss and run interaction between the selected hTf-endosome and mitochondrion (A e) proceeds from left to right at a 139-ms frame interval. Graph represents the hTf-endosomal instantaneous speed (blue line) with respect to its corresponding DT-based distance from the mitochondrion (red line) over time. Dashed box in videomicrograph and graph indicates the kiss phase. hTf-endosomal instantaneous speed is markedly reduced when it is in close proximity to the mitochondrion, denoted by the overlapping of the red line with the x axis. See Videos 6 and 7, which show two additional hTf-endosomal kiss and run events. Bar, 0.5 µm.
Mentions: To investigate the prevalence of endosome–mitochondria interactions within the early endocytic pathway, we established a criterion to quantitatively measure interactions in an unbiased and semiautomated manner. Previously, quantitative analyses of cell-to-cell (Malide et al., 2012; McKee et al., 2013) or organelle–organelle interactions (Whalen et al., 2012; Bouvet et al., 2013; Wang et al., 2015) were performed using the distance transformation (DT) algorithm. DT is a representation of the digital image in terms of pixels with assigned values based on their respective distances from the boundary of a specific object. Therefore, 3D rendering of the object in question is a prerequisite for carrying out the DT operation. Here, we used the DT algorithm, built in the image analysis software Imaris, for quantitative determination of the distance of Tf-endosomes from the boundary of 3D-rendered mitochondrial surfaces, which are considered to be the anchor organelle, as they are less dynamic than endosomes. The DT criterion was evaluated for its consistency and reliability on immunofluorescent fixed cells (Fig. 2) before it was used in the analysis of time-lapse videos to study the dynamics of endosome–mitochondria interactions in live cells (see Figs. 3, 4, and 5).

View Article: PubMed Central - HTML - PubMed

ABSTRACT

Using superresolution and quantitative fluorescence microscopy, Das et al. have revealed that iron-transferrin–containing endosomes directly interact with mitochondria, facilitating iron transfer in epithelial cells. Their findings further enrich the repertoire of organelle–organelle direct interactions to accomplish a functional significance.

No MeSH data available.


Related in: MedlinePlus