The OSBP-related protein family in humans

Oxysterols are oxygenated derivatives of cholesterol that have a number of biological effects and play a key role in the maintenance of the body chole sterol balance. In this study, we describe the cDNA sequences and genomic s tructures of the recently identified human oxysterol-binding protein (OSBP) -related protein (ORP) family (Laitinen, S. et al. 1999. J. Lipid Res. 40: 2204-2211). The family now includes 12 genes/proteins, which can be divided into six distinct subfamilies. The ORP have two major structural features: a highly conserved OSBP-type sterol-binding domain in the C-terminal half and a pleckstrin homology domain present in the N-terminal region of most f amily members. Several ORP genes are present in S. cerevisiae, D. melanogas ter, and C. elegans, suggesting that the protein family has functions of fu ndamental importance in the eukaryotic kingdom. Analysis of ORP mRNA levels in unloaded or acetylated LDI-loaded human macrophages revealed that the e xpression of ORP genes was not significantly affected by the loading, with the exception of ORP6, which was up-regulated 2-fold.ie The present study s ummarizes the basic characteristics of the OSBP-related gene/protein family in humans, and provides tools for functional analysis of the encoded prote ins.-Lehto, M., S. Laitinen, G. Chinetti, M. Johansson, C. Ehnholm, B. Stae ls, E. Ikonen, and V M. Olkkonen. The OSBP-related protein family in humans .