Type IV collagen

Collagen IV (ColIV or Col4) is a type of collagen found primarily in the basal lamina. The collagen IV C4 domain at the C-terminus is not removed in post-translational processing, and the fibers link head-to-head, rather than in parallel. Also, collagen IV lacks the regular glycine in every third residue necessary for the tight, collagen helix. This makes the overall arrangement more sloppy with kinks. These two features cause the collagen to form in a sheet, the form of the basal lamina. Collagen IV is the more common usage, as opposed to the older terminology of "type-IV collagen". Collagen IV exists in all metazoan phyla.[1]

There are six human genes associated with it:[2]

Clinical significance

The alpha-3 subunit (COL4A3) of collagen IV is thought to be the antigen implicated in Goodpasture syndrome, wherein the immune system attacks the basement membranes of the glomeruli and the alveoli upon the antigenic site on the alpha-3 subunit becomes unsequestered due to environmental exposures.

Goodpasture syndrome presents with nephritic syndrome and hemoptysis. Microscopic evaluation of biopsied renal tissue will reveal linear deposits of Immunoglobulin G by immunofluorescence. This is classically in young adult males.

Mutations to the genes coding for collagen IV lead to Alport syndrome. This will cause thinning and splitting of the glomerular basement membrane. It will present as isolated hematuria, sensorineural hearing loss, and ocular disturbances and is passed on genetically, usually in an X-linked manner, although there are rarer autosomal forms.

Liver fibrosis and cirrhosis are associated with the deposition of collagen IV in the liver. Serum Collagen IV concentrations correlate with hepatic tissue levels of collagen IV in subjects with alcoholic liver disease and hepatitis C and fall following successful therapy.[3][4]

Increased glomerular and mesangial deposition of collagen IV occurs in diabetic nephropathy and increased urinary levels are associated with the extent of renal injury.[5]

References
  1. Boute, Nicolas; Exposito, Jean-Yves; Boury-Esnault, Nicole; Vacelet, Jean; Noro, Nobuhiro; Miyazaki, Koyomi; Yoshizato, Katsutoshi; Garrone, Robert (1996). "Type IV collagen in sponges, the missing link in basement membrane ubiquity". Biology of the Cell. 88 (1–2): 37–44. doi:10.1016/S0248-4900(97)86829-3. PMID 9175266.
  2. Khoshnoodi, Jamshid; Pedchenko, Vadim; Hudson, Billy G (2008). "Mammalian collagen IV". Microscopy Research and Technique. 71 (5): 357–70. doi:10.1002/jemt.20564. PMC 4788096. PMID 18219669.
  3. Tsutsumi, Mikihiro; Takase, Shujiro; Urashima, Sachio; Ueshima, Yasuhiro; Kawahara, Hiromu; Takada, Akira (1996). "Serum Markers for Hepatic Fibrosis in Alcoholic Liver Disease: Which is the Best Marker, Type III Procollagen, Type IV Collagen, Laminin, Tissue Inhibitor of Metalloproteinase, or Prolyl Hydroxylase?". Alcoholism: Clinical and Experimental Research. 20 (9): 1512–7. doi:10.1111/j.1530-0277.1996.tb01692.x. PMID 8986196.
  4. Yabu, K; Kiyosawa, K; Mori, H; Matsumoto, A; Yoshizawa, K; Tanaka, E; Furuta, S (2009). "Serum Collagen Type IV for the Assessment of Fibrosis and Resistance to Interferon Therapy in Chronic Hepatitis C". Scandinavian Journal of Gastroenterology. 29 (5): 474–9. doi:10.3109/00365529409096841. PMID 7518613.
  5. Okonogi, H; Nishimura, M; Utsunomiya, Y; Hamaguchi, K; Tsuchida, H; Miura, Y; Suzuki, S; Kawamura, T; Hosoya, T; Yamada, K (2001). "Urinary type IV collagen excretion reflects renal morphological alterations and type IV collagen expression in patients with type 2 diabetes mellitus". Clinical nephrology. 55 (5): 357–64. PMID 11393380. INIST:985198.


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