Collagen XVIII Is a Basement Membrane Heparan Sulfate Proteoglycan*
- From the ‡Department of Neurobiology, University of Pittsburgh, Pittsburgh, Pennsylvania 15261 and¶Neurobiotechnology Center, Ohio State University, Columbus, Ohio 43210
Abstract
The present study shows that collagen XVIII is, next to perlecan and agrin, the third basal lamina heparan sulfate proteoglycan (HSPG) and the first collagen/proteoglycan with heparan sulfate side chains. By using monoclonal antibodies to an unidentified HSPG in chick, 14 cDNA clones were isolated from a chick yolk sac library. All clones had a common nucleotide sequence that was homologous to the mRNA sequences of mouse and human collagen XVIII. The deduced amino acid sequence of the chick fragment shows an 83% overall homology with the human and mouse collagen XVIII. Similar to the human and mouse homologue, the chick collagen XVIII mRNA has a size of 4.5 kilobase pairs. In Western blots, collagen XVIII appeared as a smear with a molecular mass of 300 kDa. After treatment with heparitinase, the protein was reduced in molecular mass by 120 kDa to a protein core of 180 kDa. Collagen XVIII has typical features of a collagen, such as its existence, under non-denaturing conditions, as a non-covalently linked oligomer, and a sensitivity of the core protein to collagenase digestion. It also has characteristics of an HSPG, such as long heparitinase-sensitive carbohydrate chains and a highly negative net charge. Collagen XVIII is abundant in basal laminae of the retina, epidermis, pia, cardiac and striated muscle, kidney, blood vessels, and lung. In situ hybridization showed that the main expression of collagen XVIII HSPG in the chick embryo is in the kidney and the peripheral nervous system. As a substrate, collagen XVIII moderately promoted the adhesion of Schwann cells but had no such activity on peripheral nervous system neurons and axons.
Footnotes
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↵* This work was supported by Grant NS33981-02 from the National Institutes of Health.The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
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↵§ To whom correspondence should be addressed: Dept. of Neurobiology, University of Pittsburgh, 1402 E, Biological Science Tower, Pittsburgh, PA 15261. Tel.: 412-648-9424; Fax: 412-648-1441; E-mail:whalfter{at}vms.cis.pitt.edu.
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↵2 W. Halfter, unpublished observations.
- Abbreviations:
- HSPG
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heparan sulfate proteoglycan
- E
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embryonic day
- PBS
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phosphate-buffered saline
- mAb
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monoclonal antibody
- NCAM
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neural cell adhesion molecule.
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- Received June 5, 1998.
- Revision received July 13, 1998.
- The American Society for Biochemistry and Molecular Biology, Inc.
