Type IV collagen is the major structural component of glomerular basement membranes (GBM), forming a 'chicken-wire' meshwork together with laminins, proteoglycans and entactin/nidogen.
Subcellular locations: Secreted, Extracellular space, Extracellular matrix, Basement membrane
Colocalizes with COL4A4 and COL4A5 in GBM, tubular basement membrane (TBM) and synaptic basal lamina (BL).
Expressed in Bruch's membrane, outer plexiform layer, inner nuclear layer, inner plexiform layer, ganglion cell layer, inner limiting membrane and around the blood vessels of the retina (at protein level) . Alpha 3 and alpha 4 type IV collagens are colocalized and present in kidney, eye, basement membranes of lens capsule, cochlea, lung, skeletal muscle, aorta, synaptic fibers, fetal kidney and fetal lung.  reports similar levels of expression of alpha 3 and alpha 4 type IV collagens in kidney, but  reports that in kidney levels of alpha 3 type IV collagen are significantly lower than those of alpha 4 type IV collagen. Highest levels of expression of alpha 4 type IV collagen are detected in kidney, calvaria, neuroretina and cardiac muscle. Lower levels of expression are observed in brain, lung and thymus, and no expression is detected in choroid plexus, liver, adrenal, pancreas, ileum or skin.