1. ¹McGill Cancer Center, Department of Biochemistry, McGill University, Montreal, Quebec, Canada
2. ²Division of Immunology, Shigei Medical Research Institute, Okayama, Japan
3. ³Department of Molecular Biology and Biochemistry, Okayama University Graduate School of Medicine and Dentistry, Okayama, Japan

Correspondence: Dr A Pause, McGill Cancer Center, Department of Biochemistry, McIntyre Building, 3655 Sir William Osler Promenade, Room 716, McGill University, Montreal, Quebec, Canada H3G 1Y6. E-mail: arnim.pause@mcgill.ca

Received 21 May 2007; Revised 22 June 2007; Accepted 1 July 2007; Published online 13 August 2007.

Abstract

Inactivation of the von Hippel–Lindau (VHL) tumor suppressor gene predisposes to vascular tumor formation in several organs. VHL regulates two evolutionary conserved pathways: the targeting of hydroxylated hypoxia-inducible factor- (HIF-) for proteasomal degradation and the remodeling of extracellular matrix (ECM). The biochemical mechanisms of the ECM assembly pathway remain poorly defined. Here, we provide evidence supporting a biochemical role for VHL in ECM assembly. We show that VHL directly binds to the collagen IV alpha 2 (COL4A2) chain and that this interaction is necessary for its assembly into the ECM. The VHL–COL4A2 interaction is dependent on endoplasmic reticulum (ER)-mediated COL4A2 hydroxylation and independent of cytosolic, hypoxia regulated HIF--modifying enzymes. We find that the N-terminal tail of COL4A2 protrudes from the ER lumen into the cytosol where it is bound by VHL. Failure of VHL to interact with COL4A2 correlates with loss of collagen IV network formation in vitro and collagen IV remodeling in vivo. Our data suggest a HIF--independent role for the VHL–COL4A2 interaction in suppression of angiogenic tumor formation through collagen IV network assembly.