Amphiphysin (BIN1) negatively regulates dynamin 2 for normal muscle maturation
Belinda S. Cowling, Ivana Prokic, Hichem Tasfaout, Aymen Rabai, Frédéric Humbert, Bruno Rinaldi, Anne-Sophie Nicot, Christine Kretz, Sylvie Friant, Aurélien Roux, Jocelyn Laporte
Belinda S. Cowling, Ivana Prokic, Hichem Tasfaout, Aymen Rabai, Frédéric Humbert, Bruno Rinaldi, Anne-Sophie Nicot, Christine Kretz, Sylvie Friant, Aurélien Roux, Jocelyn Laporte
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Research Article Muscle biology

Amphiphysin (BIN1) negatively regulates dynamin 2 for normal muscle maturation

Abstract

Regulation of skeletal muscle development and organization is a complex process that is not fully understood. Here, we focused on amphiphysin 2 (BIN1, also known as bridging integrator-1) and dynamin 2 (DNM2), two ubiquitous proteins implicated in membrane remodeling and mutated in centronuclear myopathies (CNMs). We generated Bin1–/– Dnm2+/– mice to decipher the physiological interplay between BIN1 and DNM2. While Bin1–/– mice die perinatally from a skeletal muscle defect, Bin1–/– Dnm2+/– mice survived at least 18 months, and had normal muscle force and intracellular organization of muscle fibers, supporting BIN1 as a negative regulator of DNM2. We next characterized muscle-specific isoforms of BIN1 and DNM2. While BIN1 colocalized with and partially inhibited DNM2 activity during muscle maturation, BIN1 had no effect on the isoform of DNM2 found in adult muscle. Together, these results indicate that BIN1 and DNM2 regulate muscle development and organization, function through a common pathway, and define BIN1 as a negative regulator of DNM2 in vitro and in vivo during muscle maturation. Our data suggest that DNM2 modulation has potential as a therapeutic approach for patients with CNM and BIN1 defects. As BIN1 is implicated in cancers, arrhythmia, and late-onset Alzheimer disease, these findings may trigger research directions and therapeutic development for these common diseases.

Authors

Belinda S. Cowling, Ivana Prokic, Hichem Tasfaout, Aymen Rabai, Frédéric Humbert, Bruno Rinaldi, Anne-Sophie Nicot, Christine Kretz, Sylvie Friant, Aurélien Roux, Jocelyn Laporte

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Figure 5

BIN1 inhibits DNM2 in an isoform-dependent manner.

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BIN1 inhibits DNM2 in an isoform-dependent manner. (A) Crystal structure...
(A) Crystal structure model of nucleotide-free human dynamin 1 (adapted from Faeber et al., ref. 52) using PyMOL. The GTPase domain (green), middle domain (light blue), and GTPase effector domain (GED, orange) forming the stalk, and the PH domain (yellow), are depicted, with the sites of DNM2 mutations linked to CNM indicated (red). The peptide encoded by 12B in human (CYYTEQLVTC) spans from position 497 (black 1), followed by 18 unresolved amino acids, and then amino acid 518 (black 2). (B) Cosedimentation assays were performed with recombinant proteins to determine protein binding (in pellet fraction) relative to total protein (pellet+soluble, see Supplemental Figure 7 for raw data), in the presence of liposomes and PIP2. Results are represented as a fold difference versus DNM2 alone. (C) Malachite green assay with DNM2 (±12B) and BIN1 (+exon 11 [Iso8] and –exon 11 [Iso9]) isoforms, with DNM2/BIN1 at a ratio of 1:4. Brain polar lipids with additional 5% PIP2 were used. Results are shown as catalytic rate (mol/mol/min). Results in B and C are an average of 2 (C) or 4 (B) independent experiments. Graph represents the mean + SEM. One-way (B and C) or 2-way (C) ANOVA test was used as described in the Methods section. *P < 0.05, **P < 0.01, ***P < 0.001.