Content area
Full Text
Mol Biol Rep (2012) 39:88838889 DOI 10.1007/s11033-012-1755-0
TM7SF1 (GPR137B): a novel lysosome integral membrane protein
Jialin Gao Libin Xia Meiqing Lu
Binhua Zhang Yueping Chen Rang Xu
Lizhuo Wang
Received: 3 December 2011 / Accepted: 7 June 2012 / Published online: 24 June 2012 Springer Science+Business Media B.V. 2012
Abstract In the previous proteomic study of human placenta, transmembrane 7 superfamily member 1 (TM7SF1) was found enriched in lysosome compartments. TM7SF1 encodes a 399-amino acid protein with a calculated molecular mass of 45 kDa. Bioinformatic analysis of its amino acid sequence showed that it is a multipass transmembrane protein containing a potential dileucine-based lysosomal targeting signal and four putative N-glycosylation sites. By percoll-gradient centrifugation and further subfraction ways, the lysosomal solute and membrane compartments were isolated respectively. Immunoblotting analysis indicated that TM7SF1 was co-fractioned with lysosome associated membrane protein 2 (LAMP2), which was only detected in lysosomal membrane compartments whereas not detected in the solute compartments. Using specic anti-TM7SF1 antibody and double-immunouorescence with lysosome membrane protein LAMP1 and Lyso-Tracker Red, the colocalisations of endogenous TM7SF1 with lysosome and late endosome markers were demonstrated. All of this indicated that TM7SF1 is an integral lysosome membrane protein. Rat ortholog of TM7SF1 was found to be
strongly expressed in heart, liver, kidney and brain while not or low detected in other tissues. In summary, TM7SF1 was a lysosomal integral membrane protein that shows tissue-specic expression. As a G-protein-coupled receptor in lysosome membrane, TM7SF1 was predicted function as signal transduction across lysosome membrane.
Keywords Integral membrane Lysosome
Subcellular location TM7SF1 Signal transduction
Introduction
The lysosome is a cytoplasmic cellular organelle with a critical role in cellular function and tissue homeostasis. The primary function of the lysosome is the degradation and recycling of macromolecules acquired by endocytosis [1], autophagy, and other cellular trafcking pathways [2]. More recently, lysosome has also been found to be highly dynamic organelles that are involved in regulating secretion [3], repairing damage to the plasma membrane [4], and forming the osteoclast rufed border [5].
To date, approximately 50 integral and peripheral membrane proteins have been identied as associated with lysosome [6]. They are thought be involved in critical functions such as presenting substrates to hydrolytic enzymes, and transporting degradation products out of lysosome [7]. The discovery...