[2FT-2] Proteomics / Protein engineering (2P-62～2P-87)

[2P-83*] Proteomic Identification and Validation of Novel Interactions of a Tumor Suppressor PRELP with the Growth Factor Receptors IGFI-R and p75NTR

^○Hirofumi Kosuge¹, Makoto Nakakido^1,2, Satoru Nagatoishi³, Tetsuya Fukuda⁴, Yasuhiko Bando⁴, Shin-ichi Ohnuma⁵, Kouhei Tsumoto^1,2,3 (1.Dept. of Chem. Biotech., Sch. of Eng., Univ. of Tokyo, 2.Dept. of Bioeng., Sch. of Eng., Univ. of Tokyo, 3.Inst. of Med. Sci., Univ. of Tokyo, 4.Biosys Technologies, 5.Inst. of Ophthalmology, Univ. College London)

The small leucine-rich repeat proteoglycans (SLRPs) are a family of secreted proteins, many of which regulate diverse cellular functions through the interactions with multiple proteins. Proline and arginine-rich end leucine-rich repeat protein (PRELP) is a SLRP, known to function as a tumor suppressor, although the molecular mechanism remains unclear. Since we hypothesized that PRELP regulates tumor cell growth through the interactions with some membrane proteins just as other SLRPs, we conducted co-immunoprecipitation coupled with mass spectrometry (CoIP-MS) to identify novel interactions of PRELP with membrane proteins. We identified novel 29 membrane proteins that would interact with PRELP, including two growth factor receptors, insulin-like growth factor I receptor (IGFI-R) and low-affinity nerve growth factor receptor (p75NTR). SPR analysis validated the direct-binding of PRELP to the extracellular domains of IGFI-R and p75NTR with micromolar affinities. We further demonstrated that PRELP suppressed the growth of A549 lung carcinoma cells also at micromolar concentration, consistent with SPR analysis. These results indicate that PRELP regulates the cellular functions through the weak interactions with these receptors.