CLAMP, a novel microtubule-associated protein with EB-type calponin homology

Cell Motil Cytoskeleton. 2005 Nov;62(3):141-56. doi: 10.1002/cm.20093.

Abstract

Microtubules (MTs) are polymers of alpha and beta tubulin dimers that mediate many cellular functions, including the establishment and maintenance of cell shape. The dynamic properties of MTs may be influenced by tubulin isotype, posttranslational modifications of tubulin, and interaction with microtubule-associated proteins (MAPs). End-binding (EB) family proteins affect MT dynamics by stabilizing MTs, and are the only MAPs reported that bind MTs via a calponin-homology (CH) domain (J Biol Chem 278 (2003) 49721-49731; J Cell Biol 149 (2000) 761-766). Here, we describe a novel 27 kDa protein identified from an inner ear organ of Corti library. Structural homology modeling demonstrates a CH domain in this protein similar to EB proteins. Northern and Western blottings confirmed expression of this gene in other tissues, including brain, lung, and testis. In the organ of Corti, this protein localized throughout distinctively large and well-ordered MT bundles that support the elongated body of mechanically stiff pillar cells of the auditory sensory epithelium. When ectopically expressed in Cos-7 cells, this protein localized along cytoplasmic MTs, promoted MT bundling, and efficiently stabilized MTs against depolymerization in response to high concentration of nocodazole and cold temperature. We propose that this protein, designated CLAMP, is a novel MAP and represents a new member of the CH domain protein family.

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Blotting, Northern
  • COS Cells
  • Calcium-Binding Proteins / chemistry
  • Calcium-Binding Proteins / genetics*
  • Calcium-Binding Proteins / metabolism
  • Calponins
  • Chlorocebus aethiops
  • Cloning, Molecular
  • Conserved Sequence
  • Cytoskeletal Proteins / chemistry
  • Cytoskeletal Proteins / genetics
  • Cytoskeletal Proteins / metabolism
  • Gene Expression Profiling
  • Humans
  • Mice
  • Microfilament Proteins
  • Microscopy, Electron, Scanning
  • Microtubule-Associated Proteins / chemistry
  • Microtubule-Associated Proteins / genetics*
  • Microtubule-Associated Proteins / metabolism
  • Microtubules / metabolism*
  • Models, Molecular
  • Molecular Sequence Data
  • Organ of Corti / metabolism
  • Polymerase Chain Reaction
  • Rats
  • Sequence Homology, Amino Acid
  • Tubulin / genetics
  • Tubulin / metabolism

Substances

  • Calcium-Binding Proteins
  • Cytoskeletal Proteins
  • Microfilament Proteins
  • Microtubule-Associated Proteins
  • Tubulin