type IV collagen
Summary
Type IV collagen is the primary structural component of basement membranes, forming a sheet-like network that provides support for epithelial and endothelial cells. It is composed of α3, α4, and α5 chains in the glomerular basement membrane, and mutations in these chains cause hereditary nephritis syndromes.
Detail
Type IV collagen is a unique collagen type that forms the structural backbone of basement membranes throughout the body. Unlike fibrillar collagens (types I, II, III), type IV collagen forms a two-dimensional network rather than fibrils. It consists of six different α chains (α1-α6) that combine to form three main heterotrimers: α1α1α2 (most common), α3α4α5 (kidney, lung, ear), and α5α5α6 (skin, smooth muscle). The α3α4α5 network is particularly important in the glomerular basement membrane (GBM), where it provides filtration barrier integrity. Mutations in COL4A5 (X-linked) cause Alport syndrome, characterized by progressive nephritis, sensorineural hearing loss, and ocular abnormalities. COL4A3 and COL4A4 mutations cause autosomal forms of Alport syndrome. Anti-GBM antibodies targeting the α3 chain cause Goodpasture syndrome, leading to rapidly progressive glomerulonephritis and pulmonary hemorrhage. Type IV collagen is also found in the blood-brain barrier, alveolar basement membranes, and other epithelial basement membranes, making it crucial for tissue integrity and cellular function.
Sources
- Robbins Basic Pathology
- First Aid for the USMLE Step 1
- Kumar & Clark's Clinical Medicine
- Harrison's Principles of Internal Medicine
- Pathoma
Reviewed by AnkiBoss editorial — medical student review. Information here is for study reference only and is not medical advice. Spotted an error? Let us know.