ID 26990
Author
Azuma, Hiroyuki First Department of Internal Medicine, The University of Tokushima School of Medicine
Keywords
Hereditary hemorrhagic telangiectasia
endoglin
ALK
TGF-β
Smad
Content Type
Journal Article
Description
Hereditary hemorrhagic telangiectasia (HHT) is an autosomal dominant disorder characterized by vascular dysplasia and hemorrhage. The pathogenesis regarding heterogeneity of vascular malformations in patients with HHT has been obscure, although it has become possible to partially explain the pathogenesis from the identification of two distinct genes, endoglin and ALK-1. Endoglin and ALK-1 are type III and type I TGF-β receptors, respectively, and are exclusively expressed on vascular endothelial cells. Binding of TGF-β to the type II TGF-β receptor on endothelial cells, which is accelerated in the presence of endoglin, phosphorylates type I TGF-β receptors, ALK-5 and ALK-1, and phosphorylated ALK-5 and ALK-1 activate the downstream proteins Smad2/3 and Smad1/5, respectively. These activated Smad proteins dissociate from the type I TGF-β receptor, bind to Smad4, and enter the nucleus to transmit TGF-β signaling by regulating transcription from specific gene promoters involved in angiogenesis. Therefore, a balance between these two signaling pathways via ALK-5 and ALK-1 plays an important role in determining the properties of endothelial cells during angiogenesis.
Mutations of endoglin and ALK-1 genes are genetic pathogenesis of HHT type 1 and HHT type 2, respectively. To date, at least 29 and 17 different kinds of mutations in endoglin and ALK-1, respectively, have been found, including missense, nonsense, frameshift, and deletion mutations. The precise mechanisms of vascular abnormalities elicited by these mutations observed in HHT patients are still uncertain, although elucidation of the mechanism of intracellular signal transduction and the change in targeted gene expressions using mutant recombinant endoglin or ALK-1 proteins and knockout mice will enable us to understand the genetic and molecular pathogenesis of HHT and to effectively treat patients with HHT.
Journal Title
The journal of medical investigation : JMI
ISSN
13431420
NCID
AA11166929
Volume
47
Issue
3-4
Start Page
81
End Page
90
Sort Key
81
Published Date
2000
Remark
EDB ID
FullText File
language
eng