Crystal Structure of Human Leukocyte Cell-derived Chemotaxin 2 (LECT2) Reveals a Mechanistic Basis of Functional Evolution in a Mammalian Protein with an M23 Metalloendopeptidase Fold

Abstract

Human leukocyte cell-derived chemotaxin 2 (LECT2), which is predominantly expressed in the liver, is a multifunctional protein. LECT2 is becoming a potential therapeutic target for several diseases of worldwide concern such as rheumatoid arthritis, hepatocellular carcinoma, and obesity. Here, we present the crystal structure of LECT2, the first mammalian protein whose structure contains an M23 metalloendopeptidase fold. The LECT2 structure adopts a conserved Zn(II) coordination configuration but lacks a proposed catalytic histidine residue, and its potential substratebinding groove is blocked in the vicinity of the Zn(II)-binding site by an additional intrachain loop at the N terminus. Consistent with these structural features, LECT2 was found to be catalytically inactive as a metalloendopeptidase against various types of peptide sequences, including pentaglycine. In addition, a surface plasmon resonance analysis demonstrated that LECT2 bound to the c-Met receptor with micromolar affinity. These results indicate that LECT2 likely plays its critical roles by acting as a ligand for the corresponding protein receptors rather than as an enzymatically active peptidase. The intrachain loop together with the pseudoactive site groove in LECT2 structure may be specific for interactions between LECT2 and receptors. Our study reveals a mechanistic basis for the functional evolution of a mammalian protein with an M23 metalloendopeptidase fold and potentially broadens the implications for the biological importance of noncatalytic peptidases in the M23 family.Leukocyte cell-derived chemotaxin 2 (LECT2) 2 is a secretory protein originally identified as a chemotactic factor for neutrophils (1). LECT2 is predominantly expressed in the liver and is a direct target gene of Wnt/␤-catenin signaling (2-6). Accumulating evidence shows that mammalian LECT2 is a multifunctional protein that is closely associated with several diseases of worldwide concern, including hepatitis (7), rheumatoid arthritis (8 -10), hepatocellular carcinoma (HCC) (11, 12), obesity (13,14), and renal and hepatic amyloidosis (15-17). It has been reported that concanavalin A-induced hepatitis and collagen antibody-induced arthritis were suppressed by LECT2 (7,8). In addition, LECT2 expression inhibited the migration and invasion of human HCC cells in vitro and was negatively correlated with vascular invasion and tumor recurrence in HCC patients (11). In contrast, serum LECT2 levels were positively correlated with the severity of obesity and fatty liver in humans, and overproduction of LECT2 caused the development of obesity-associated insulin resistance (13,14). These findings suggest that LECT2 may be a candidate prognostic marker and a potential therapeutic target for these diseases. Despite the importance of LECT2 functions, the underlying mechanisms remain largely unclear.The mature human LECT2 is a basic protein consisting of 133 amino acids. Sequence similarity searches using BLAST have shown that LECT2 has a putative peptidase-M23 (PF01551) domain located ...

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“…The initial phase of ULam111 SeMet was obtained using single anomalous dispersion (SAD) 36 . After selenium atom search and phase calculations with PHENIX AutoSol Wizard in the PHENIX program suite 37 , model building was automatically carried out with PHENIX AutoBuild Wizard 37 .…”

“…The structure of native ULam111 was determined by the molecular replacement method using the MOLREP program 39 , 40 with the ULam111 SeMet structure as the initial model. Manual rebuilding and refinement of native ULam111 was performed with COOT 36 and PHENIX.REFINE 37 , respectively. The geometry of the final structure was evaluated with the program Rampage 41 .…”

Leukocyte Cell‐Derived Chemotaxin‐2: It's Role in Pathophysiology and Future in Clinical Medicine

“…In fact, mice that died at 24 h in the Escherichia coli model had lower levels of circulating LECT2 (15.21 ± 1.03 ng/mL vs. 22.02 ± 1.22 ng/mL; P < 0.001) which may correlate with humans studies that we will discuss below . In that same study, recombinant LECT2 administration at a concentration of 30–135 ng/mg improved mouse survival from these models when compared with normal saline . Dang et al .…”

“…There are three disulfide bonds between six evolutionarily conserved cysteine residues . The crystal structure of LECT2 was recently identified by Zheng et al . ( Figure ).…”

Neurodevelopment: Three’s a Crowd, Four Is a Receptor Complex

“…The PVD dendritic outgrowth function of LECT-2 is disabled by missense mutations that alter key conserved residues in the M23 domain, but further work is required to determine if LECT-2 enzymatic activity is involved [4]. The mammalian LECT2 protein was originally identified as a chemotactic and growth factor [17,18], but its M23 domain lacks peptidase activity and may function strictly as a protein-protein interaction domain [19]. Intriguing recent evidence implicates mammalian LECT2 in dendrite outgrowth [20].…”