8.A.191.  The Translocon-associated Protein Subunit beta (TPSβ) Family 

The translocon-associated protein (TRAP) subunit, beta (TPSβ) family includes the SSR2 protein of 183 aas and 2 TMSs at the N- and C-termini of the protein. TRAP proteins are parts of a complex whose function is to bind calcium to the ER membrane and thereby regulate the retention of ER resident proteins. It is an SRP-dependent cotranslational protein, targeting its substrates to the membrane (Chen et al. 2022). Signal Sequence Receptor Subunit 2 (SSR2) is a key endoplasmic reticulum gene involved in protein folding and processing. It is upregulated in several cancers, and the expression of the SSR2 gene in hepatocellular carcinoma (HCC) tissues has been noted. The expression of SSR2 is increased in HCC tissues, and SSR2 expression is associated with several clinical characteristics. SSR2 is probably involved in signalling pathways related to the G2/M checkpoint, passive transmembrane transporter activity, and ncRNA metabolic process. SSR2 knockdown inhibits cell proliferation, migration and invasive ability and promoted apoptosis and cell cycle arrest in vitro. Moreover, downregulation of SSR2 also repressed the growth of HepG2 cells in vivo, suggesting that the SSR2 gene is an oncogene in HCC (Chen et al. 2022).