Figure 5. Panel A shows a microscopic... | Rockefeller University Press

Figure 5.

$MYCT1 is a transmembrane phosphoglycoprotein that interacts with IFITM2/3. (A) Endogenous MYCT1 is located at cell–cell junctions (arrow) and in puncta (arrowhead). Staining of human primary ECs for MYCT1 (black), VE-cadherin (magenta), and DNA (blue). Scale bar, 10 µm. (B) MYCT1 is a membrane protein. Western blot analysis of various EC fractions for MYCT1, GAPDH, PECAM1, H3K27ac, and vimentin proteins. Cy, cytoplasm; Mb, membrane; Nu, nucleus; Ck, cytoskeleton. (C) MYCT1 is glycosylated. Western blot analysis of MYCT1 protein electrophoretic mobility in control and PNGase-F–treated lysates. (D) Schematic model of MYCT1 structure and domains with phosphorylation sites, identified by mass spectrometry. MYCT1 phosphorylation sites are highly conserved as indicated by the color scale. Asterisks indicate sites also described at https://www.phosphosite.org/. (E) Top five proteins interacting with MYCT1 as identified by mass spectrometry, among which IFITM2 and IFITM3. ECs were transduced with recombinant adenoviruses to transiently overexpress MYCT1 or GFP, as a control. Cell lysates were collected 48 h after transduction, immunoprecipitated using MYCT1 antibody or a control IgG, and analyzed by mass spectrometry. Proteins interacting with both endogenous and overexpressed MYCT1 were selected and ranked by normalized spectral abundance factor (NSAF) from two independent mass spectrometry (MS) experiments are shown (31 proteins); the top five proteins are highlighted in magenta. (F) GO terms of the cellular component and biological process overrepresented in the MYCT1 interactome. Fisher’s exact test with adjustment for false discovery rate (FDR). (G) Validation of IFITM2/3 and MYCT1 interaction by co-IP. EC lysates from confluent ECs were immunoprecipitated (IP) with MYCT1 or control IgG and blotted for IFITM2/3. H, IgG heavy chain; L, IgG light chain. (H) IFITM2/3 are constitutively expressed in ECs in vitro and in vivo. Staining of human primary ECs (upper panels), human brain and WAT sections (lower panels) for MYCT1 (gray), IFITM2/3 (green), VE-cadherin (magenta), and DNA (blue). Scale bar, 20 µm (brain) and 50 µm (adipose tissue). (I) MYCT1 and IFITM2/3 interact in brain ECs. Proximity ligation assay (PLA) in human brain sections. Detection of PLA dots (gray) in ECs and staining for VE-cadherin (magenta) and DNA (blue). Arrowheads, colocalization of MYCT1::IFITM2/3 PLA dots and VE-cadherin staining. Scale bar, 20 µm. See also Fig. S4. Source data are available for this figure: SourceData F5. Refer to the image caption for details.$ Panel A shows a microscopic image of human primary endothelial cells stained for M Y C T 1 (black), V E-cadherin (magenta), and D N A (blue), highlighting M Y C T 1's location at cell-cell junctions and in puncta. Panel B presents a Western blot analysis of various endothelial cell fractions for M Y C T 1, G A P D H, P E C A M 1, H 3 K 2 7 a c, and vimentin proteins, indicating M Y C T 1 as a membrane protein. Panel C shows a Western blot analysis of M Y C T 1 protein electrophoretic mobility, demonstrating M Y C T 1 glycosylation. Panel D is a schematic model of M Y C T 1 structure and domains with phosphorylation sites. Panel E is a scatter plot identifying the top five proteins interacting with M Y C T 1, including I F I T M 2 and I F I T M 3, as determined by mass spectrometry. Panel F displays gene ontology terms of cellular components and biological processes. Panel G validates the interaction between I F I T M 2 slash 3 and M Y C T 1 through Co-I P. Panel H shows staining of human primary endothelial cells, human brain, and white adipose tissue sections for M Y C T 1, I F I T M 2 slash 3, V E-cadherin, and D N A. Panel I presents a proximity ligation assay in human brain sections detecting M Y C T 1 and F I T M 2 slash 3 interaction in endothelial cells.

MYCT1 is a transmembrane phosphoglycoprotein that interacts with IFITM2/3. (A) Endogenous MYCT1 is located at cell–cell junctions (arrow) and in puncta (arrowhead). Staining of human primary ECs for MYCT1 (black), VE-cadherin (magenta), and DNA (blue). Scale bar, 10 µm. (B) MYCT1 is a membrane protein. Western blot analysis of various EC fractions for MYCT1, GAPDH, PECAM1, H3K27ac, and vimentin proteins. Cy, cytoplasm; Mb, membrane; Nu, nucleus; Ck, cytoskeleton. (C) MYCT1 is glycosylated. Western blot analysis of MYCT1 protein electrophoretic mobility in control and PNGase-F–treated lysates. (D) Schematic model of MYCT1 structure and domains with phosphorylation sites, identified by mass spectrometry. MYCT1 phosphorylation sites are highly conserved as indicated by the color scale. Asterisks indicate sites also described at https://www.phosphosite.org/. (E) Top five proteins interacting with MYCT1 as identified by mass spectrometry, among which IFITM2 and IFITM3. ECs were transduced with recombinant adenoviruses to transiently overexpress MYCT1 or GFP, as a control. Cell lysates were collected 48 h after transduction, immunoprecipitated using MYCT1 antibody or a control IgG, and analyzed by mass spectrometry. Proteins interacting with both endogenous and overexpressed MYCT1 were selected and ranked by normalized spectral abundance factor (NSAF) from two independent mass spectrometry (MS) experiments are shown (31 proteins); the top five proteins are highlighted in magenta. (F) GO terms of the cellular component and biological process overrepresented in the MYCT1 interactome. Fisher’s exact test with adjustment for false discovery rate (FDR). (G) Validation of IFITM2/3 and MYCT1 interaction by co-IP. EC lysates from confluent ECs were immunoprecipitated (IP) with MYCT1 or control IgG and blotted for IFITM2/3. H, IgG heavy chain; L, IgG light chain. (H) IFITM2/3 are constitutively expressed in ECs in vitro and in vivo. Staining of human primary ECs (upper panels), human brain and WAT sections (lower panels) for MYCT1 (gray), IFITM2/3 (green), VE-cadherin (magenta), and DNA (blue). Scale bar, 20 µm (brain) and 50 µm (adipose tissue). (I) MYCT1 and IFITM2/3 interact in brain ECs. Proximity ligation assay (PLA) in human brain sections. Detection of PLA dots (gray) in ECs and staining for VE-cadherin (magenta) and DNA (blue). Arrowheads, colocalization of MYCT1::IFITM2/3 PLA dots and VE-cadherin staining. Scale bar, 20 µm. See also Fig. S4. Source data are available for this figure: SourceData F5.