Scube2 enhances proteolytic Shh processing from the surface of Shh-producing cells
JOURNAL OF CELL SCIENCE
Authors: Jakobs, Petra; Exner, Sebastian; Schuermann, Sabine; Pickhinke, Ute; Bandari, Shyam; Ortmann, Corinna; Kupich, Sabine; Schulz, Philipp; Hansen, Uwe; Seidler, Daniela G.; Grobe, Kay
Abstract
All morphogens of the Hedgehog (Hh) family are synthesized as dual-lipidated proteins, which results in their firm attachment to the surface of the cell in which they were produced. Thus, Hh release into the extracellular space requires accessory protein activities. We suggested previously that the proteolytic removal of N- and C-terminal lipidated peptides (shedding) could be one such activity. More recently, the secreted glycoprotein Scube2 (signal peptide, cubulin domain, epidermal-growth-factor-like protein 2) was also implicated in the release of Shh from the cell membrane. This activity strictly depended on the CUB domains of Scube2, which derive their name from the complement serine proteases and from bone morphogenetic protein-1/tolloid metalloproteinases (C1r/C1s, Uegf and Bmp1). CUB domains function as regulators of proteolytic activity in these proteins. This suggested that sheddases and Scube2 might cooperate in Shh release. Here, we confirm that sheddases and Scube2 act cooperatively to increase the pool of soluble bioactive Shh, and that Scube2-dependent morphogen release is unequivocally linked to the proteolytic processing of lipidated Shh termini, resulting in truncated soluble Shh. Thus, Scube2 proteins act as protease enhancers in this setting, revealing newly identified Scube2 functions in Hh signaling regulation.
HcCUB-Lec, a newly identified C-type lectin that contains a distinct CUB domain and participates in the immune defense of the triangle sail mussel Hyriopsis cumingii
DEVELOPMENTAL AND COMPARATIVE IMMUNOLOGY
Authors: Huang, Ying; Ren, Qian
Abstract
As pattern recognition receptors (PRRs), C-type lectins (CTLs) play crucial roles in recognizing and eliminating pathogens in innate immunity. In this study, a novel CTL (HcCUB-Lec) was identified from the triangle sail mussel Hyriopsis cumingii. The full-length of HcCUB-Lec cDNA was 1558 bp with an open reading frame of 1281 bp that encodes a putative protein of 426 amino acid residues, including an N-terminal signal peptide, a complement Uegf Bmp1 (CUB) domain, a single carbohydrate recognition domain (CRD), and a transmembrane domain. Quantitative real-time PCR analysis revealed that HcCUB-Lec transcript was distributed in all examined tissues with the highest levels in hepatopancreas and was significantly upregulated in gills and hepatopancreas after immune challenge with Staphyloccocus aureus and Vibrio parahaemolyticus. When HcCUB-Lec was silenced by RNAi, the expression levels of three antimicrobial peptides, including whey acidic protein (HcWAP), defensin (HcDef), and lysozyme (HcLyso), were dramatically decreased in gills. The recombinant HcCUB-Lec and its individual CUB and CRD domains can bind with Gram-positive bacteria (S. aureus and Bacillus subtilis), Gram-negative bacteria (V. parahaemolyticus and Aeromonas hydrophila), and polysaccharides (lipopolysaccharide and peptidoglycan). Moreover, rHcCUB-Lec and its domains could also agglutinate S. aureus and V. parahaemolyticus in the presence of Ca2+ and can clear V. parahaemolyticus in H. cumingii. Results of this study suggest that HcCUB-Lec acts as an antimicrobial PRR that participates in the innate immune responses of H. cumingii.