SOCS3 acts as a potential negative regulator in the antiviral response of large yellow croaker (Larimichthys crocea) by interacting with STAT1

Abstract

Suppressors of cytokine signaling (SOCS) proteins are important regulators of the Janus kinase-signal transducer and activator of transcription (JAK-STAT) pathway. Within the SOCS family, SOCS3 is one of the most potent inhibitors of cytokine signaling. However, there is limited knowledge regarding the function of SOCS3 on regulating type I interferon (IFN) signaling in fish. In this study, the complete open reading frame (ORF) of SOCS3 from the large yellow croaker (Larimichthys crocea, LcSOCS3) was cloned and characterized. The ORF of LcSOCS3 was 618 nucleotides in length and encoded a protein containing 205 amino acids. LcSOCS3 had the typical domain architecture of the SOCS family, including an SRC homology 2 (SH2) domain, a SOCS box, an additional kinase inhibition region (KIR), and an extended SH2 subdomain (ESS). Phylogenetic analysis revealed that LcSOCS3 was clustered with other fish SOCS3s and most closely related to the SOCS3 of Collichthy lucidus. LcSOCS3 mRNA was detected in all organs or tissues examined, and its expression was significantly increased in both head kidney and spleen tissues, and primary head kidney leukocytes after poly(I:C) stimulation. Overexpression of LcSOCS3 significantly promoted Spring viremia of carp virus (SVCV) replication, resulting in a more severe cytopathic effect, increased viral titer, enhanced copy number of the SVCV-G gene, and decreased expression levels of IFN1, IRF7, ISG15, Viperin, PKR, and Mx in epithelioma papulosum cyprinid (EPC) cells. Silencing of LcSOCS3 correspondingly up-regulated the expression of IFNi, IFNh, PKR, Viperin, and Mx in large yellow croaker head kidney (LYCK) cells. Additionally, LcSOCS3 was shown to interact with Signal Transducer and Activator of Transcription 1 (STAT1) which may inhibit STAT1 translocating into the nucleus. This speculation was supported by the increased phosphorylation level of STAT1 in head kidney leukocytes after LcSOCS3 silencing. These results indicated that LcSOCS3 functioned as a potential negative regulator of type I IFN signaling in large yellow croaker through its interaction with STAT1.