SPRY domain-containing SOCS box protein 4 (SPSB4)

SPSB4 (SPRY domain-containing SOCS box protein 4) is an adaptor protein that forms part of a Cullin5-based E3 ubiquitin ligase complex, characterized by a central SPRY domain for substrate recognition and a C-terminal SOCS box domain for ubiquitin ligase assembly[1][2][7][8]. SPSB4 targets proteins, including NOS2, NR1D1, and EphB2, for ubiquitination and subsequent proteasomal degradation, thereby regulating nitric oxide production in macrophages, circadian transcriptional repressors, and EphB2-dependent cell signaling[4][7][8][9]. Dysregulation or mutation of SPSB4 is implicated in pathways relevant to inflammation, cancer (e.g., affecting apoptosis regulators like Par-4), and other diseases[1][7][9]. SPSB4 is a validated molecular target for modulating ubiquitin-proteasome degradation in selected cellular processes.

Other names

SplA/ryanodine receptor domain and SOCS box containing 4SPSB4SSB4SSB-4SPRY domain-containing SOCS box protein SSB-4

Ubiquitination and proteasomal degradation of substrate proteins, such as NOS2 (inducible nitric oxide synthase), NR1D1 (nuclear receptor involved in circadian rhythm), and EphB2 (receptor tyrosine kinase)