integrin alpha-7 (ITGA7)
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Function
- associates with integrin beta-1 (integrin alpha-7/beta-1)
- isoform alpha-7X2B & isoform alpha-7X1B promote myoblast migration on laminin 1 & laminin 2/4, but isoform alpha-7X1B is less active on laminin 1 (in vitro)
Structure
- composed of an heavy & a light chain linked by a disulfide bond
- ADP-ribosylated on at least two sites of the extracellular domain in skeletal myotubes (putative)
- belongs to the integrin alpha chain family
- contains 7 FG-GAP repeats
Compartment
membrane
Alternative splicing
- named isoforms=12
- additional isoforms seem to exist
- at least 5 alternatively spliced domains, 3 extracellular (X1, X2 & D) & 3 cytoplasmic (A, B & C)
Expression
- isoforms containing segment A are predominantly expressed in skeletal muscle
- isoforms containing segment B are abundantly expressed in skeletal muscle, moderately in cardiac muscle, small intestine, colon, ovary & prostate & weakly in lung & testes
- isoforms containing segment X2D are expressed at low levels in fetal & adult skeletal muscle & in cardiac muscle, but are not detected in myoblasts & myotubes
- in muscle fibers isoforms containing segment A & B are expressed at myotendinous & neuromuscular junctions
- isoforms containing segment C are expressed at neuromuscular junctions & at extrasynaptic sites
- isoforms containing segments X1 or X2 or, at low levels
- X1X2 isoforms are expressed in fetal & adult skeletal muscle (myoblasts & myotubes) & cardiac muscle
- in renewing intestinal epithelium, expression of isoforms containing segment B correlates with the onset of enterocytic differentiation
Pathology
- defects in ITGA7 are associated with congenital myopathy due to ITGA7 defect