FERM Domain Containing Protein 3 (FRMD3)

Protein 4.1 of red blood cells, or 4.1R (EPB41), is a multifunctional protein essential for maintaining erythrocyte shape and membrane mechanical properties. The 553-amino acid 4.1O protein shares 38% identity with the 4.1B protein and contains a FERM domain. PCR analysis of 16 human tissues showed expression of 4.1O only in ovary. In 8 human fetal tissues, expression could be detected in skeletal muscle, with lower levels in thymus and brain. FRMD3 was expressed in normal human lung tissue, but it was silenced in 54 of 58 primary nonsmall cell lung carcinomas. Loss of FRMD3 expression did not correlate with specific tumor stage, and FRMD3 was not downregulated in other tumor types examined. FRMD3 overexpression in human epithelial cells reduced clonogenicity by inducing apoptosis.