CARMIL is a potent capping protein antagonist: Identification of a conserved CARMIL domain that inhibits the activity of capping protein and uncaps capped actin filaments

Takehito Uruno, Kirsten Remmert, John A. Hammer

研究成果: ジャーナルへの寄稿学術誌査読

50 被引用数 (Scopus)

抄録

Acanthamoeba CARMIL was previously shown to co-purify with capping protein (CP) and to bind pure CP. Here we show that this interaction inhibits the barbed end-capping activity of CP. Even more strikingly, this interaction drives the uncapping of actin filaments previously capped with CP. These activities are CP-specific; CARMIL does not inhibit the capping activities of either gelsolin or CapG and does not uncap gelsolin-capped filaments. Although full-length (FL) CARMIL (residues 1-1121) possesses both anti-CP activities, C-terminal fragments like glutathione S-transferase (GST)-P (940-1121) that contain the CARMIL CP binding site are at least 10 times more active. We localized the full activities of GST-P to its C-terminal 51 residues (1071-1121). This sequence contains a stretch of 25 residues that is highly conserved in CARMIL proteins from protozoa, flies, worms, and vertebrates (CARMIL Homology domain 3; CAH3). Point mutations showed that the majority of the most highly conserved residues within CAH3 are critical for the anti-CP activity of GST-AP (862-1121). Finally, we found that GST-AP binds CP ∼20-fold more tightly than does FL-CARMIL. This observation together with the elevated activities of C-terminal fragments relative to FL-CARMIL suggests that FL-CARMIL might exist primarily in an autoinhibited state. Consistent with this idea, proteolytic cleavage of FL-CARMIL with thrombin generated an ∼14-kDa C-terminal fragment that expresses full anti-CP activities. We propose that, after some type of physiological activation event, FL-CARMIL could function in vivo as a potent CP antagonist. Given the pivotal role that CP plays in determining the global actin phenotype of cells, our results suggest that CARMIL may play an important role in the physiological regulation of actin assembly.

本文言語英語
ページ(範囲)10635-10650
ページ数16
ジャーナルJournal of Biological Chemistry
281
15
DOI
出版ステータス出版済み - 4月 14 2006
外部発表はい

!!!All Science Journal Classification (ASJC) codes

  • 生化学
  • 分子生物学
  • 細胞生物学

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