Lcrd (also known as leucine-rich repeat domain containing) is a protein family that is found in a variety of proteins involved in cell adhesion, receptor signaling, and cytoskeletal organization. The Lcrd protein family consists of four members: L1, L2, L3, and L4. All four members are type I transmembrane proteins with the N-terminus located outside of the cell and the C-terminus located inside of the cell.
The four members of the Lcrd protein family share a common structure consisting of an extracellular region that contains several leucine-rich repeats (LRRs). These LRRs are believed to be responsible for mediating protein-protein interactions. The intracellular region of each protein contains a tail that is believed to be involved in signal transduction.
The exact function of each member of the Lcrd protein family is not fully understood, but it is thought that they play roles in cell adhesion, migration, proliferation, and differentiation. For example, mutations in the gene encoding for L1 have been linked to increased risk for various cancers such as breast cancer and ovarian cancer. Additionally, mutations in the gene encoding for L2 have been linked to neurodevelopmental disorders such as autism spectrum disorder and intellectual disability.