<p>Regulated expression of Kruppel like factor (KLF) transcription factors is essential for normal maintenance of endothelial cells, but loss of either K-Rev interaction trapped 1 (KRIT1) or cerebral cavernous malformations 2 (CCM2) proteins results in significant over-expression of KLF4 protein, causing the cerebrovascular disorder, cerebral cavernous malformations. Here, combining knockdown and reconstitution in an endothelial cell line, with co-immunoprecipitation, biophysical analysis of purified proteins, and co-crystallography, we find that to restrain KLF4 expression, two CCM2 proteins must cluster on a single KRIT1, with the PTB domain of each CCM2 protein binding either the second or third NPxF motif within KRIT1. This clustering of two PTB domains to a single peptide reveals a previously unobserved mechanism for PTB domain recruitment to partner proteins. Overall, our data support a model where clustering of two CCM2 molecules to one KRIT1 is required for normal regulation of expression of KLF4 transcription factor.</p>

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Dual recruitment of two CCM2 molecules to KRIT1 suppresses KLF4 expression

  • Clotilde Huet-Calderwood,
  • Oriana S. Fisher,
  • Sreya Das,
  • Valerie L. Su,
  • Titus J. Boggon,
  • David A. Calderwood

摘要

Regulated expression of Kruppel like factor (KLF) transcription factors is essential for normal maintenance of endothelial cells, but loss of either K-Rev interaction trapped 1 (KRIT1) or cerebral cavernous malformations 2 (CCM2) proteins results in significant over-expression of KLF4 protein, causing the cerebrovascular disorder, cerebral cavernous malformations. Here, combining knockdown and reconstitution in an endothelial cell line, with co-immunoprecipitation, biophysical analysis of purified proteins, and co-crystallography, we find that to restrain KLF4 expression, two CCM2 proteins must cluster on a single KRIT1, with the PTB domain of each CCM2 protein binding either the second or third NPxF motif within KRIT1. This clustering of two PTB domains to a single peptide reveals a previously unobserved mechanism for PTB domain recruitment to partner proteins. Overall, our data support a model where clustering of two CCM2 molecules to one KRIT1 is required for normal regulation of expression of KLF4 transcription factor.