Cell Biology Section, Neurogenetics Branch, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD 20892, USA.
Mol Biol Cell. 2012 Nov;23(22):4347-61. doi: 10.1091/mbc.E12-04-0292. Epub 2012 Sep 26.
Diverse cellular processes, including multivesicular body formation, cytokinesis, and viral budding, require the sequential functions of endosomal sorting complexes required for transport (ESCRTs) 0 to III. Of these multiprotein complexes, ESCRT-III in particular plays a key role in mediating membrane fission events by forming large, ring-like helical arrays. A number of proteins playing key effector roles, most notably the ATPase associated with diverse cellular activities protein VPS4, harbor present in microtubule-interacting and trafficking molecules (MIT) domains comprising asymmetric three-helical bundles, which interact with helical MIT-interacting motifs in ESCRT-III subunits. Here we assess comprehensively the ESCRT-III interactions of the MIT-domain family member MITD1 and identify strong interactions with charged multivesicular body protein 1B (CHMP1B), CHMP2A, and increased sodium tolerance-1 (IST1). We show that these ESCRT-III subunits are important for the recruitment of MITD1 to the midbody and that MITD1 participates in the abscission phase of cytokinesis. MITD1 also dimerizes through its C-terminal domain. Both types of interactions appear important for the role of MITD1 in negatively regulating the interaction of IST1 with VPS4. Because IST1 binding in turn regulates VPS4, MITD1 may function through downstream effects on the activity of VPS4, which plays a critical role in the processing and remodeling of ESCRT filaments in abscission.
多种细胞过程，包括多泡体形成、胞质分裂和病毒出芽，都需要内体分选复合物运输所需的连续功能（ESCRTs）0 到 III。在这些多蛋白复合物中，ESCRT-III 特别在通过形成大的、环形螺旋阵列来介导膜分裂事件方面发挥关键作用。许多发挥关键效应作用的蛋白质，特别是与多种细胞活动相关的 ATP 酶 VPS4，具有微管相互作用和运输分子（MIT）结构域，包括不对称的三螺旋束，与 ESCRT-III 亚基中的螺旋 MIT 相互作用基序相互作用。在这里，我们全面评估了 MIT 结构域家族成员 MITD1 与 ESCRT-III 的相互作用，并鉴定了与带电多泡体蛋白 1B（CHMP1B）、CHMP2A 和增加的钠耐受-1（IST1）的强相互作用。我们表明，这些 ESCRT-III 亚基对于 MITD1 向中体的募集是重要的，并且 MITD1 参与胞质分裂的分离阶段。MITD1 还通过其 C 端结构域二聚化。这两种类型的相互作用对于 MITD1 负调控 IST1 与 VPS4 相互作用的作用似乎都很重要。因为 IST1 结合反过来调节 VPS4，MITD1 可能通过对 VPS4 活性的下游影响起作用，VPS4 在分离过程中 ESCRT 纤维的加工和重塑中起着关键作用。
