Journal Article

The ESCRT-III pathway facilitates cardiomyocyte release of cBIN1-containing microparticles

Liu, Yan, Baum, Rachel, Hong, TingTing, Fu, Ying, Agvanian, Sosse, Zhou, Kang, Wirka, Robert C., Xu, Bing, Shaw, Robin M.

2017

Overview

Microparticles (MPs) are cell-cell communication vesicles derived from the cell surface plasma membrane, although they are not known to originate from cardiac ventricular muscle. In ventricular cardiomyocytes, the membrane deformation protein cardiac bridging integrator 1 (cBIN1 or BIN1+13+17) creates transverse-tubule (t-tubule) membrane microfolds, which facilitate ion channel trafficking and modulate local ionic concentrations. The microfold-generated microdomains continuously reorganize, adapting in response to stress to modulate the calcium signaling apparatus. We explored the possibility that cBIN1-microfolds are externally released from cardiomyocytes. Using electron microscopy imaging with immunogold labeling, we found in mouse plasma that cBIN1 exists in membrane vesicles about 200 nm in size, which is consistent with the size of MPs. In mice with cardiac-specific heterozygous Bin1 deletion, flow cytometry identified 47% less cBIN1-MPs in plasma, supporting cardiac origin. Cardiac release was also evidenced by the detection of cBIN1-MPs in medium bathing a pure population of isolated adult mouse cardiomyocytes. In human plasma, osmotic shock increased cBIN1 detection by enzyme-linked immunosorbent assay (ELISA), and cBIN1 level decreased in humans with heart failure, a condition with reduced cardiac muscle cBIN1, both of which support cBIN1 release in MPs from human hearts. Exploring putative mechanisms of MP release, we found that the membrane fission complex endosomal sorting complexes required for transport (ESCRT)-III subunit charged multivesicular body protein 4B (CHMP4B) colocalizes and coimmunoprecipitates with cBIN1, an interaction enhanced by actin stabilization. In HeLa cells with cBIN1 overexpression, knockdown of CHMP4B reduced the release of cBIN1-MPs. Using truncation mutants, we identified that the N-terminal BAR (N-BAR) domain in cBIN1 is required for CHMP4B binding and MP release. This study links the BAR protein superfamily to the ESCRT pathway for MP biogenesis in mammalian cardiac ventricular cells, identifying elements of a pathway by which cytoplasmic cBIN1 is released into blood.

• Publisher: Public Library of Science,Public Library of Science (PLoS)
• Subject: Actin / Adaptor Proteins, Signal Transducing - blood / Adaptor Proteins, Signal Transducing - chemistry / Adaptor Proteins, Signal Transducing - genetics / Adaptor Proteins, Signal Transducing - metabolism / Alzheimer's disease / Animals / BAR protein / Bathing / Biology / Biology and Life Sciences / Blood plasma / Calcium / Calcium signalling / Cardiac muscle / Cardiomyocytes / Cell interactions / Cell signaling / Cell surface / Cell-Derived Microparticles - chemistry / Cell-Derived Microparticles - metabolism / Cell-Derived Microparticles - ultrastructure / Cells, Cultured / Clonal deletion / Cytometry / Data collection / Deformation / Deformation mechanisms / Electron microscopy / Endosomal Sorting Complexes Required for Transport - antagonists & inhibitors / Endosomal Sorting Complexes Required for Transport - blood / Endosomal Sorting Complexes Required for Transport - chemistry / Endosomal Sorting Complexes Required for Transport - genetics / Endosomal Sorting Complexes Required for Transport - metabolism / Endosomal Sorting Complexes Required for Transport - ultrastructure / Enzyme-Linked Immunosorbent Assay / Enzymes / Exons / Fission / Flow cytometry / Health aspects / Heart / Heart cells / Heart diseases / Heart failure / Heart Failure - blood / Heart Failure - pathology / HeLa Cells / Heterozygote / Humans / Ion channels / Medicine / Medicine and Health Sciences / Membrane proteins / Membrane vesicles / Membranes / Mice, Transgenic / Microparticles / Microscopy, Electron, Transmission / Muscles / Mutants / Myocytes, Cardiac - cytology / Myocytes, Cardiac - metabolism / Myocytes, Cardiac - pathology / Myocytes, Cardiac - ultrastructure / Nerve Tissue Proteins - blood / Nerve Tissue Proteins - chemistry / Nerve Tissue Proteins - genetics / Nerve Tissue Proteins - metabolism / Neurosciences / Nuclear Proteins - blood / Nuclear Proteins - chemistry / Nuclear Proteins - genetics / Nuclear Proteins - metabolism / Osmotic shock / Particle Size / Peptide Fragments - blood / Peptide Fragments - chemistry / Peptide Fragments - metabolism / Physicians / Physiology / Plasma / Plasmas (physics) / Protein Interaction Domains and Motifs / Protein Transport / Proteins / Recombinant Proteins - chemistry / Recombinant Proteins - metabolism / Research and analysis methods / RNA Interference / Tumor Suppressor Proteins - blood / Tumor Suppressor Proteins - chemistry / Tumor Suppressor Proteins - genetics / Tumor Suppressor Proteins - metabolism / Ventricle / Vesicles