Molecular aspects and transcriptional analysis of SH2-domain containing leukocyte protein from black rockfish (Sebastes schlegelii)

Adapter molecules, which can be found in every cell type, contribute vitally in signal transduction. These are multi-domain proteins which are lacking with intrinsic catalytic activity. However, their function is facilitating via nucleating molecular complexes during signal transduction. The SLP-76 family of adapters has three members, each expressed exclusively in hematopoietic cells-SH2 domain containing leukocyte phosphoprotein of 76 kDa, B cell linker protein (BLNK/BASH/BCA/SLP-65) and cytokine-dependent hemopoietic cell linker (Clnk/MIST). Here in, we have characterized the molecular aspects of SH2-domain containing leukocyte protein where it is also known as Lymphocyte cytosolic protein 2 (LCP2) from black rockfish (RfLCP2). Web based bioinformatics tools were used for the analyzing of domain architecture of the SH2- domain containing leukocyte protein. According to the in silico analysis this protein has a molecular weight of 55.66 kDa and a theoretical pI value of 7.29. Domain architecture analysis revealed that this protein has a conserved SH2 domain which is important for the cell signaling transduction process. Moreover there are conserved polypeptide binding sites including; phosphotyrosine binding pockets and hydrophobic binding pockets. Moreover, two N-glycosylation sites were observed in the putative protein sequence. Absence of signal peptide suggested that this protein does not have any secretory properties with it. Multiple sequence alignment with its known orthologs revealed highly conserved residues in the RfLCP2 protein. Identity similarity analysis confirmed that RfLCP2 shared the highest identity percentage with Larimichthys crocea with a percentage of 78 %. Ubiquitous expression was observed in RfLCP2 transcripts in healthy rock fish tissues with different magnitudes. However, the immense expression was observed in the blood tissue. Immune responsive function of RfLCP2 was evaluated with immune challenged tissues. According to the transcriptional analysis, the highest expression of RfLCP2 was observed in 24h post infection against Streptococcus iniae. However, at the 12 h time point RfLCP2 was highly up-regulated against LPS. Upon viral infection (against Poly I:C) RfLCP2 was possessed the highest up-regulation at 12h pi. Collectively, we can suggest that RfLCP2 play an important role in the immune responsive function in black rockfish.