6UZK

Crystal Structure of the Ternary Complex of KRIT1 bound to both the Rap1 GTPase and HKi6


Experimental Data Snapshot

  • Method: X-RAY DIFFRACTION
  • Resolution: 1.92 Å
  • R-Value Free: 0.286 
  • R-Value Work: 0.220 

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This is version 1.2 of the entry. See complete history


Literature

Inhibition of the HEG1-KRIT1 interaction increases KLF4 and KLF2 expression in endothelial cells.

Lopez-Ramirez, M.A.McCurdy, S.Li, W.Haynes, M.K.Hale, P.Francisco, K.Oukoloff, K.Bautista, M.Choi, C.H.J.Sun, H.Gongol, B.Shyy, J.Y.Ballatore, C.Sklar, L.A.Gingras, A.R.

(2021) FASEB Bioadv 3: 334-355

  • DOI: 10.1096/fba.2020-00141
  • Primary Citation of Related Structures:  
    6UZK

  • PubMed Abstract: 
  • The transmembrane protein heart of glass1 (HEG1) directly binds to and recruits Krev interaction trapped protein 1 (KRIT1) to endothelial junctions to form the HEG1-KRIT1 protein complex that establishes and maintains junctional integrity. Genetic inactivation or knockdown of endothelial HEG1 or KRIT1 leads to the upregulation of transcription factors Krüppel-like factors 4 and 2 (KLF4 and KLF2), which are implicated in endothelial vascular homeostasis; however, the effect of acute inhibition of the HEG1-KRIT1 interaction remains incompletely understood ...

    The transmembrane protein heart of glass1 (HEG1) directly binds to and recruits Krev interaction trapped protein 1 (KRIT1) to endothelial junctions to form the HEG1-KRIT1 protein complex that establishes and maintains junctional integrity. Genetic inactivation or knockdown of endothelial HEG1 or KRIT1 leads to the upregulation of transcription factors Krüppel-like factors 4 and 2 (KLF4 and KLF2), which are implicated in endothelial vascular homeostasis; however, the effect of acute inhibition of the HEG1-KRIT1 interaction remains incompletely understood. Here, we report a high-throughput screening assay and molecular design of a small-molecule HEG1-KRIT1 inhibitor to uncover acute changes in signaling pathways downstream of the HEG1-KRIT1 protein complex disruption. The small-molecule HEG1-KRIT1 inhibitor 2 (HKi2) was demonstrated to be a bona fide inhibitor of the interaction between HEG1 and KRIT1 proteins, by competing orthosterically with HEG1 through covalent reversible interactions with the FERM (4.1, ezrin, radixin, and moesin) domain of KRIT1. The crystal structure of HKi2 bound to KRIT1 FERM revealed that it occupies the same binding pocket on KRIT1 as the HEG1 cytoplasmic tail. In human endothelial cells (ECs), acute inhibition of the HEG1-KRIT1 interaction by HKi2 increased KLF4 and KLF2 mRNA and protein levels, whereas a structurally similar inactive compound failed to do so. In zebrafish, HKi2 induced expression of klf2a in arterial and venous endothelium. Furthermore, genome-wide RNA transcriptome analysis of HKi2-treated ECs under static conditions revealed that, in addition to elevating KLF4 and KLF2 expression, inhibition of the HEG1-KRIT1 interaction mimics many of the transcriptional effects of laminar blood flow. Furthermore, HKi2-treated ECs also triggered Akt signaling in a phosphoinositide 3-kinase (PI3K)-dependent manner, as blocking PI3K activity blunted the Akt phosphorylation induced by HKi2. Finally, using an in vitro colocalization assay, we show that HKi6, an improved derivative of HKi2 with higher affinity for KRIT1, significantly impedes recruitment of KRIT1 to mitochondria-localized HEG1 in CHO cells, indicating a direct inhibition of the HEG1-KRIT1 interaction. Thus, our results demonstrate that early events of the acute inhibition of HEG1-KRIT1 interaction with HKi small-molecule inhibitors lead to: (i) elevated KLF4 and KLF2 gene expression; and (ii) increased Akt phosphorylation. Thus, HKi's provide new pharmacologic tools to study acute inhibition of the HEG1-KRIT1 protein complex and may provide insights to dissect early signaling events that regulate vascular homeostasis.


    Organizational Affiliation

    Department of Medicine University of California San Diego La Jolla CA USA.



Macromolecules
Find similar proteins by:  (by identity cutoff)  |  Structure
Entity ID: 1
MoleculeChainsSequence LengthOrganismDetailsImage
Krev interaction trapped protein 1A322Homo sapiensMutation(s): 0 
Gene Names: KRIT1CCM1
UniProt & NIH Common Fund Data Resources
Find proteins for O00522 (Homo sapiens)
Explore O00522 
Go to UniProtKB:  O00522
PHAROS:  O00522
Protein Feature View
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  • Reference Sequence
Find similar proteins by:  (by identity cutoff)  |  Structure
Entity ID: 2
MoleculeChainsSequence LengthOrganismDetailsImage
Ras-related protein Rap-1bB167Homo sapiensMutation(s): 0 
Gene Names: RAP1BOK/SW-cl.11
EC: 3.6.5.2
UniProt & NIH Common Fund Data Resources
Find proteins for P61224 (Homo sapiens)
Explore P61224 
Go to UniProtKB:  P61224
PHAROS:  P61224
Protein Feature View
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  • Reference Sequence
Small Molecules
Ligands 3 Unique
IDChainsName / Formula / InChI Key2D Diagram3D Interactions
GNP (Subject of Investigation/LOI)
Query on GNP

Download Ideal Coordinates CCD File 
E [auth B]PHOSPHOAMINOPHOSPHONIC ACID-GUANYLATE ESTER
C10 H17 N6 O13 P3
UQABYHGXWYXDTK-UUOKFMHZSA-N
 Ligand Interaction
QMA (Subject of Investigation/LOI)
Query on QMA

Download Ideal Coordinates CCD File 
C [auth A]2-hydroxy-6-methoxynaphthalene-1-carbaldehyde
C12 H10 O3
OTNKCGQLSHSABI-UHFFFAOYSA-N
 Ligand Interaction
MG
Query on MG

Download Ideal Coordinates CCD File 
D [auth B]MAGNESIUM ION
Mg
JLVVSXFLKOJNIY-UHFFFAOYSA-N
 Ligand Interaction
Experimental Data & Validation

Experimental Data

  • Method: X-RAY DIFFRACTION
  • Resolution: 1.92 Å
  • R-Value Free: 0.286 
  • R-Value Work: 0.220 
  • Space Group: P 1 21 1
Unit Cell:
Length ( Å )Angle ( ˚ )
a = 57.204α = 90
b = 77.089β = 91.558
c = 58.41γ = 90
Software Package:
Software NamePurpose
REFMACrefinement
HKL-2000data reduction
HKL-2000data scaling
PHASERphasing

Structure Validation

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Ligand Structure Quality Assessment  



Entry History & Funding Information

Deposition Data

  • Deposited Date: 2019-11-15 
  • Released Date: 2020-11-18 
  • Deposition Author(s): Gingras, A.R.

Funding OrganizationLocationGrant Number
Other governmentUnited StatesMRP-17-454909
Other governmentUnited StatesDE-AC02-05CH11231

Revision History  (Full details and data files)

  • Version 1.0: 2020-11-18
    Type: Initial release
  • Version 1.1: 2021-03-31
    Changes: Database references
  • Version 1.2: 2021-05-26
    Changes: Database references