Members of the suppressor of cytokine signaling (SOCS) family of proteins
contain C-terminal regions of homology called the SOCS box, which serves
to couple SOCS proteins and their binding partners with the Elongin B and C
complex, thereby mediating protein degradation. Several other families of
proteins also contain SOCS boxes, but differ from the SOCS proteins in the
type of domain they contain upstream of the SOCS box. SSB-2 (SplA/ryanodine
(SPRY) receptor domain-containing SOCS box protein 2), also known as
GGRCC9 (gene-rich cluster protein C9), SPSB2 or MGC2519, is a cytoplasmic
protein belonging to the SPSB family of proteins that contain a central SPRY
domain and a C-terminal SOCS box. The SPRY domain is believed to be a
protein-protein interaction motif. Members of the SPSB family are capable
of interacting with Met (a receptor for hepatocyte growth factors (HGFs)), and
SSB-1 is known to promote HGF signaling. SSB-1, SSB-2 and SSB-4 are also
able to interact with PAR4 (prostate apoptosis response protein 4). Mutations
in the genes encoding SPSB proteins are associated with several human diseases.