Identification and characterization of a novel L-type lectin (MjLTL2) from kuruma shrimp (Marsupenaeus japonicus)

Abstract

L-type lectins (LTLs) belong to the lectin family and are characterized by a conserved structural motif in their carbohydrate recognition domain. LTLs are homologous to leguminous lectins. In this study, we identified and functionally characterized an LTL from kuruma shrimp Marsupenaeus japonicus. We designated this LTL as MjLTL2. MjLTL2 contains a signal peptide, a Lectin_leg domain, a coiled coil, and transmembrane domain. MjLTL2 is distributed in hemocytes, heart, hepatopancreas, gill, stomach, and intestine; higher expression levels are seen in hemocytes and the hepatopancreas than in other tissues. MjLTL2 was upregulated following challenge of shrimp with Vibrio anguillarum and white spot syndrome virus (WSSV). MjLTL2 can agglutinate several bacteria without Ca 2+ . In addition, MjLTL2 could bind to several Gram-positive and -negative bacteria by binding to their lipopolysaccharide and peptidoglycan. However, MjLTL2 could not enhance the clearance of V. anguillarum in vivo. In the presence of WSSV infection, MjLTL2 knockdown by RNA interference resulted in a 7day lower cumulative mortality of M. japonicus. Moreover, less VP19, VP24, VP26, and VP28 mRNAs were extracted from the hemocytes of MjLTL2 knockdown shrimp than from the control. These results suggest that MjLTL2 is involved in immune responses in shrimp.

The role of pattern recognition receptors in crustacean innate immunity

“…While M. rosenbergii VIP36 could protect the host against WSSV infection by inhibiting WSSV replication in vivo, LTL2 from P. japonicus was required for WSSV proliferation. 150,152 Confirming the latter results, the LTL from P. clarkii was also found to enhance the multiplication of WSSV. 155 Hence, the role of LTL in the immune activity of crustaceans is interesting, but the mechanisms of regulation of viral proliferation and multiplications need to be further elucidated.…”

“…Antiviral participation of LTLs has been noticed in some studies supported by contrasting evidence have been supported. While M. rosenbergii VIP36 could protect the host against WSSV infection by inhibiting WSSV replication in vivo, LTL2 from P. japonicus was required for WSSV proliferation 150,152 . Confirming the latter results, the LTL from P. clarkii was also found to enhance the multiplication of WSSV 155 .…”

“…and LTL2) could efficiently agglutinate several bacterial species, including V. anguillarum and Vibrio harveyi accelerating their clearance from the host system. [148][149][150] The same functional activity was also attributed to E. sinensis LTLs (ERGIC-53 and VIP36) and M. rosenbergii VIP36 that was required for efficient clearing of V. parahaemolyticus and S. aureus based on growth inhibition and agglutination studies. 151,152 The LTL isolated from P. trituberculatus could bind to LPS suggesting its participation in the immune response against Gram-positive and Gram-negative bacteria.…”

“…The innate immune function of LTLs has been richly explored in crustacean models with specific reference to anti‐bacterial participation. The LTL from P. japonicus (LTL1, LTLC1 and LTL2) could efficiently agglutinate several bacterial species, including V. anguillarum and Vibrio harveyi accelerating their clearance from the host system 148–150 . The same functional activity was also attributed to E. sinensis LTLs (ERGIC‐53 and VIP36) and M. rosenbergii VIP36 that was required for efficient clearing of V. parahaemolyticus and S. aureus based on growth inhibition and agglutination studies 151,152 .…”