Characterization of a human rhomboid homolog, p100hRho/RHBDF1, which interacts with TGF-alpha family ligands.
The activity of the TGF-alpha-like ligand Spitz in Drosophila depends on Rhomboid, a seven-transmembrane spanning protein that resides in the Golgi and acts as a serine protease to cleave Spitz, thereby releasing the soluble ligand. Several rhomboids in Drosophila have been implicated in the processing of TGF-alpha-like ligands, and consequent EGF receptor activation. The larger number of TGF-alpha-like ligands in vertebrates raises the possibility that they too might be subject to regulation by rhomboid-like proteins. We present the cDNA cloning and polypeptide sequence of an atypically long human rhomboid, which, based on the absence of critical residues for serine protease activity, is not predicted to act as a serine protease. We examined its tissue distribution, in comparison with TGF-alpha and the TGF-alpha-related protein HB-EGF, and the EGF/TGF-alpha receptor, in mouse embryo. This rhomboid, named p100(hRho) or RHBDF1, is a seven-transmembrane protein with a long N-terminal cytoplasmic extension that comprises half of the polypeptide sequence, and is found in the endoplasmic reticulum and Golgi, but not on the cell surface. It is expressed as two forms with different lengths, forms dimers and interacts with TGF-alpha ligands through a luminal interaction with the EGF core ectodomain. Finally, we evaluated the function of p100(hRho)/RHBDF1 in Drosophila, demonstrating that the short, but not the full-length form has functional activity. The characterization of this protein extends our understanding of the rhomboid family of regulatory proteins.
Nakagawa
Takatoshi
T
Department of Cell and Tissue Biology, Program in Cell Biology, University of California at San Francisco, San Francisco, California 94143-0512, USA.
Guichard
Annabel
A
Castro
Carolina Perez
CP
Xiao
Yang
Y
Rizen
Michael
M
Zhang
Hong-Zhong
HZ
Hu
Diane
D
Bang
Anne
A
Helms
Jill
J
Bier
Ethan
E
Derynck
Rik
R
D000595:Amino Acid Sequence; D000818:Animals; D002462:Cell Membrane / Q000737:chemistry / Q000378:metabolism; D019281:Dimerization; D004330:Drosophila / Q000502:physiology; D066246:ErbB Receptors / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D008024:Ligands; D008565:Membrane Proteins; D051379:Mice; D008969:Molecular Sequence Data; D005810:Multigene Family; D009928:Organ Specificity; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism; D017434:Protein Structure, Tertiary; D016211:Transforming Growth Factor alpha / Q000378:metabolism*
D008024:Ligands; D008565:Membrane Proteins; D020033:Protein Isoforms; C081962:RHBDF1 protein, human; D016211:Transforming Growth Factor alpha; D066246:ErbB Receptors