small integral membrane protein 5 (SMIM5) of CASIMO1
This family contains the small integral membrane protein 5 (SMIM5) variant of the Cancer-Associated Small Integral Membrane Open reading frame 1 (CASIMO1), a small open reading frame (sORF)-encoded protein (also known as a microprotein). CASIMO1 controls cell proliferation and interacts with squalene epoxidase (SQLE) modulating lipid droplet formation. CASIMO1 RNA is overexpressed predominantly in hormone receptor-positive breast tumors, and its knockdown has been shown to decrease proliferation in multiple breast cancer cell lines. Loss of CASIMO1 disturbs the organization of the actin cytoskeleton, leads to inhibition of cell motility, and stalls the cell cycle in the G0/G1 phase. CASIMO1 interacts with SQLE, a key enzyme in cholesterol synthesis and a known oncogene in breast cancer. This variant is expressed on chromosome 16 in humans, mostly in the stomach, kidney, thyroid and esophagus.
Jiyao W et al.(2023). "The conserved domain database in 2023.",