What is "actinin"

n. (context protein English) Any of several microfilament proteins that have a function in the attachment of actin fibres in muscle cells

Actinin is a microfilament protein. α-Actinin is necessary for the attachment of actin filaments to the Z-lines in skeletal muscle cells, and to the dense bodies in smooth muscle cells. The functional protein is an anti-parallel dimer, which cross-links the thin filaments in adjacent sarcomeres, and therefore coordinates contractions between sarcomeres in the horizontal axis.

The non-sarcomeric α-actinins, encoded by ACTN1 and ACTN4, are widely expressed. ACTN2 expression is found in both cardiac and skeletal muscle, whereas ACTN2 is limited to the latter. Both ends of the rod-shaped α-actinin dimer contain actin-binding domains.

Mutations in ACTN4 can cause the kidney disease focal segmental glomerulosclerosis (FSGS).