Contents lists available at ScienceDirect Fish and Shellfish Immunology journal homepage: www.elsevier.com/locate/fsi Full length article The effect of the lectin from Cherax quadricarinatus on its granular hemocytes José Luis Sánchez-Salgado a,b,* , Mohamed Alí Pereyra a , Concepción Agundis a , Oscar Vivanco-Rojas a , Carlos Rosales c , Cristina Pascual d , Juan José Alpuche-Osorno e , Edgar Zenteno a,f a Departamento de Bioquímica, Facultad de Medicina, Universidad Nacional Autónoma de México, Mexico City, Mexico b Posgrado de Ciencias del Mar y Limnología, Universidad Nacional Autónoma de México, Mexico City, Mexico c Departamento de Inmunología, Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México, Mexico City, Mexico d Unidad Multidisciplinaria de Docencia e Investigación, Facultad de Ciencias, Universidad Nacional Autónoma de México, Sisal, Yucatán, Mexico e CONACYT-Facultad de Medicina y Cirugía, Universidad Autónoma Benito Juárez de Oaxaca, Oaxaca, Mexico f Centro de Investigaciones, Facultad de Medicina UNAM-Universidad Autónoma Benito Juárez de Oaxaca, Oaxaca, Mexico ARTICLE INFO Keywords: Signaling pathways Hemocyte activation Cherax quadricarinatus Immune system Lectins Membrane receptor ABSTRACT In crustaceans, lectins and hemocytes of the innate immune system provide the first line of defense. Although evidence points to the potential role of lectins in regulating hemocyte activity, the processes underlying the lectin activation have not been evaluated. In the present study, the receptor for CqL, a humoral lectin from Cherax quadricarinatus specific for galactose/sialic acid, was identified in a granular subset of hemocytes. The CqL receptor (CqLR) is a 490-kDa glycoprotein, composed of four identical 120-kDa subunits. As shown by immunohistochemistry, CqL at 7.5 μg/mL as optimal dose, after 2 min, induced, specifically on granular he- mocytes, increased phosphorylation of serine (152%), threonine (192%), and tyrosine (242%) as compared with non-treated hemocytes; moreover, CqL induced increased generation of reactive oxygen species (ROS). Specific kinase inhibitors showed inhibition (P < 0.001) of ROS production induced by CqL. These results strongly suggest that CqL actively participated in the generation of ROS through kinases induced by a CqLR in a subset of granular hemocytes of the crayfish C. quadricarinatus. The results provide strong evidence that CqL activates, through specific granular hemocytes, receptors that modulate cellular functions in C. quadricarinatus. 1. Introduction Numerous mechanisms are involved in the elimination of pathogens in crustaceans [1]. Humoral immunity includes the prophenoloxidase system, antimicrobial peptides, and lectins [2]. Cellular immunity in the hemolymph of crustaceans is accomplished mainly by three cellular populations of hemocytes: granular, semi-granular, and hyaline [3]. The main functions of hemocytes are encapsulation, phagocytosis, and oxidative burst [4,5]. These cells utilize pattern recognition receptors to identify pathogen-associated molecular patterns of groups of micro- organisms [6,7]. Several studies have suggested that serum lectins participate in the regulation of immune mechanisms in crustaceans [8]. Previous reports have identified the presence of glycosylated homo-receptors for serum lectins in crustacean hemocytes and described their role in activation of the immunological process [9–12]. In C. quadricarinatus serum, A lectin, CqL, with specificity for sialic acid, galactose, and glycoproteins con- taining sialylated O-glycosidically linked glycans, such as bovine sub- maxillary mucin, has been purified by affinity chromatography [13]. Moreover, it has been showed that CqL recognizes its own hemocytes, and this interaction seems to be mediated by recognition of glycosy- lated sites of its own membrane receptor [13]. In crustaceans, serum lectins show the capacity to induce reactive oxygen species (ROS) production in hemocytes; however, it is not clear which signaling molecules are involved [9,10]. In mammals, several molecules have been pointed out that participate in activating the NADPH complex and produce ROS, the most relevant molecules are kinases such as phosphatidylinositol 3-kinase (PI3K), protein kinase C https://doi.org/10.1016/j.fsi.2018.03.050 Received 15 December 2017; Received in revised form 15 March 2018; Accepted 28 March 2018 * Corresponding author. Facultad de Medicina - UNAM, Ciudad de México, 04510, Mexico. E-mail address: jlsanchezsalgado@gmail.com (J.L. Sánchez-Salgado). Fish and Shellfish Immunology 77 (2018) 131–138 Available online 29 March 2018 1050-4648/ © 2018 Elsevier Ltd. All rights reserved. T