The membrane-tubulating potential of amphiphysin 2/BIN1 is dependent on the microtubule-binding cytoplasmic linker protein 170 (CLIP-170)

Eur J Cell Biol. 2009 Feb;88(2):91-102. doi: 10.1016/j.ejcb.2008.08.006. Epub 2008 Nov 12.

Abstract

Amphiphysins are BIN-amphiphysin-RVS (BAR) domain-containing proteins that influence membrane curvature in sites such as T-tubules in muscular cells, endocytic pits in neuronal as well as non-neuronal cells, and possibly cytoplasmic endosomes. This effect on lipid membranes is fulfilled by diverse amphiphysin 2/BIN1 isoforms, generated by alternative splicing and showing distinct structural and functional properties. In this study, our goal was to characterize the functional role of a ubiquitously expressed amphiphysin 2/BIN1 by the characterization of new molecular partners. We performed a two-hybrid screen with an isoform of amphiphysin 2/BIN1 expressed in HeLa cells. We identified CLIP-170 as an amphiphysin 2/BIN1-interacting molecule. CLIP-170 is a plus-end tracking protein involved in microtubule (MT) stability and recruitment of dynactin. The binding between amphiphysin 2/BIN1 and CLIP-170 is dependent on the N-terminal part of amphiphysin 2 (mostly the BAR domain) and an internal coiled-coil region of CLIP-170. This partnership was confirmed by GST pull-down assay and by co-immunoprecipitation in HeLa cells that express endogenous amphiphysin 2 (mostly isoforms 6, 9 and 10). When overexpressed in HeLa cells, amphiphysin 2/BIN1 leads to the formation of intracellular tubules which can closely align with MTs. After MT depolymerization by nocodazole, amphiphysin 2-stained tubules disappear, and reappear after nocodazole washout. Furthermore, depletion of CLIP-170 by RNAi induced a decrease in the proportion of cells with amphiphysin 2-stained tubules and an increase in the proportion of cells with no tubules. This result suggests the existence of a mechanistic link between the two types of tubules, which is likely to involve the +TIP protein, CLIP-170. Amphiphysin 2/BIN1 may be an anchoring point on membranes for CLIP-170, and consequently for MT. Then, the pushing force of polymerizing MT could help amphiphysin 2/BIN1 in its tubulation potential. We propose that amphiphysin 2/BIN1 participates in the tubulation of traffic intermediates and intracellular organelles first via its intrinsic tubulating potential and second via its ability to bind CLIP-170 and MT.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Cell Membrane / drug effects
  • Cell Membrane / metabolism*
  • Cell Surface Extensions / drug effects
  • Cell Surface Extensions / metabolism*
  • Gene Expression Regulation / drug effects
  • HeLa Cells
  • Humans
  • Intracellular Space / drug effects
  • Intracellular Space / metabolism
  • Microtubule-Associated Proteins / chemistry
  • Microtubule-Associated Proteins / metabolism*
  • Microtubules / drug effects
  • Microtubules / metabolism*
  • Neoplasm Proteins / chemistry
  • Neoplasm Proteins / metabolism*
  • Nerve Tissue Proteins / chemistry
  • Nerve Tissue Proteins / genetics
  • Nerve Tissue Proteins / metabolism*
  • Nocodazole / pharmacology
  • Protein Binding / drug effects
  • Protein Isoforms / chemistry
  • Protein Isoforms / genetics
  • Protein Isoforms / metabolism
  • Protein Structure, Tertiary
  • Protein Transport / drug effects
  • Tubulin / metabolism
  • Two-Hybrid System Techniques

Substances

  • Microtubule-Associated Proteins
  • Neoplasm Proteins
  • Nerve Tissue Proteins
  • Protein Isoforms
  • Tubulin
  • amphiphysin
  • cytoplasmic linker protein 170
  • Nocodazole