CLT1 targets angiogenic endothelium through CLIC1 and fibronectin.
Angiogenesis is important for tumor growth and metastasis. CLT1 (CGLIIQKNEC), a peptide that binds to tumor interstitial spaces in the presence of fibrin-fibronectin, has structural similarity to the anti-angiogenic β-sheet peptides anastellin and anginex. This similarity is reflected in the ability of CLT1 to form co-aggregates with fibronectin that induce an unfolded protein response and cause autophagic cell death in proliferating endothelial cells. CLT1 cytotoxicity is mediated at least in parts by a novel CLT1 binding protein, Chloride Intracellular Channel 1 (CLIC1), which promotes internalization of CLT1-fibronectin co-aggregates in a mechanism that depends on the LIIQK amino acid sequence of CLT1. LIIQK encompasses amino acid residues relevant for CLT1 binding to CLIC1 and in addition, facilitates the formation of CLT1-fibronectin co-aggregates, which in turn promote translocation of CLIC1 to the endothelial cell surface through ligation of integrin αvβ3. Paralleling the in vitro results, we found that CLT1 co-localizes with CLIC1 and fibronectin in angiogenic blood vessels in vivo, and that CLT1 treatment inhibited angiogenesis and tumor growth. Our findings show that CLT1 is a new anti-angiogenic compound, and its mechanism of action is to form co-aggregates with fibronectin, which bind to angiogenic endothelial cells through integrins, become internalized through CLIC1 and elicit a cytotoxic unfolded protein response. The simple structure and high potency of CLT1 make it a potentially useful compound for anti-angiogenic treatments.
Department of Urology, University of Pittsburgh School of Medicine, Shadyside Medical Center, Suite G33, 5200 Centre Avenue, Pittsburgh, PA 15232, USA.
Lynn M
LM
Knowles
Gunjan
G
Malik
Brian L
BL
Hood
Thomas P
TP
Conrads
Jan
J
Pilch
D000595:Amino Acid Sequence; D020533:Angiogenesis Inhibitors / Q000737:chemistry / Q000494:pharmacology / Q000627:therapeutic use; D000818:Animals; D000970:Antineoplastic Agents / Q000737:chemistry / Q000494:pharmacology / Q000627:therapeutic use; D016923:Cell Death / Q000187:drug effects; D045744:Cell Line, Tumor; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D049109:Cell Proliferation / Q000187:drug effects; D018118:Chloride Channels / Q000378:metabolism*; D004705:Endocytosis / Q000187:drug effects; D004730:Endothelium, Vascular / Q000187:drug effects* / Q000378:metabolism*; D005353:Fibronectins / Q000737:chemistry / Q000378:metabolism*; D061307:Human Umbilical Vein Endothelial Cells / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D006801:Humans; D008247:Lysosomes / Q000187:drug effects / Q000378:metabolism; D008297:Male; D051379:Mice; D008819:Mice, Nude; D008969:Molecular Sequence Data; D009389:Neovascularization, Pathologic / Q000188:drug therapy / Q000473:pathology; D018919:Neovascularization, Physiologic / Q000187:drug effects*; D010456:Peptides, Cyclic / Q000737:chemistry / Q000494:pharmacology* / Q000627:therapeutic use; D020836:Protein Structure, Quaternary
D020533:Angiogenesis Inhibitors; D000970:Antineoplastic Agents; C501966:CLIC1 protein, human; D018118:Chloride Channels; D005353:Fibronectins; D010456:Peptides, Cyclic; C510872:cyclo(cysteinyl-glycyl-leucyl-isoleucyl-isoleucyl-glutaminyl-lysyl-asparaginyl-glutamyl-cysteinyl)