Chondroitin sulfate proteoglycans of bovine cornea: structural characterization and assessment for the adherence of Plasmodium falciparum-infected erythrocytes Rajeshwara N. Achur a , Arivalagan Muthusamy a , Subbarao V. Madhunapantula a , Veer P. Bhavanandan a , Clement Seudieu b , D. Channe Gowda a, * a Department of Biochemistry and Molecular Biology, Pennsylvania State University College of Medicine, 500 University Drive, Hershey, PA 17033, USA b Department of Biochemistry and Molecular Biology, Georgetown University Medical Center, Washington, DC 20007, USA Received 4 February 2004; received in revised form 27 May 2004; accepted 17 June 2004 Available online 14 July 2004 Abstract The structures of the bovine corneal chondroitin sulfate (CS) chains and the nature of core proteins to which these chains are attached have not been studied in detail. In this study, we show that structurally diverse CS chains are present in bovine cornea and that they are mainly linked to decorin core protein. DEAE-Sephacel chromatography fractionated the corneal chondroitin sulfate proteoglycans (CSPGs) into three distinct fractions, CSPG-I, CSPG-II, and CSPG-III. These CSPGs markedly differ in their CS and dermatan sulfate (DS) contents, and in particular the CS structure—the overall sulfate content and 4- to 6-sulfate ratio. In general, the CS chains of the corneal CSPGs have low to moderate levels (15–64%) of sulfated disaccharides and 0–30% DS content. Structural analysis indicated that the DS disaccharide units in the CS chains are segregated as large blocks. We have also assessed the suitability of the corneal CSPGs as an alternative to placental CSPG or the widely used bovine tracheal chondroitin sulfate A (CSA) for studying the structural interactions involved in the adherence of Plasmodium falciparum-infected red blood cells (IRBCs) to chondroitin 4-sulfate. The data demonstrate that the corneal CSPGs efficiently bind IRBCs, and that the binding strength is either comparable or significantly higher than the placental CSPG. In contrast, the IRBC binding strength of bovine tracheal CSA is markedly lower than the human placental and bovine corneal CSPGs. Thus, our data demonstrate that the bovine corneal CSPG but not tracheal CSA is suitable for studying structural interactions involved in IRBC-C4S binding. D 2004 Elsevier B.V. All rights reserved. Keywords: Bovine cornea; Chondroitin sulfate proteoglycan; Decorin; Characterization; Plasmodium falciparum binding 1. Introduction The proteoglycans of the corneal stroma have been reported to comprise chondroitin sulfate/dermatan sulfate proteoglycans (CS/DSPGs) and keratan sulfate proteogly- cans (KSPGs) [1,2]. Approximately 99% of the uronic-acid- containing proteoglycan of the bovine cornea has been reported to represent decorin and the remainder biglycan [1,3–5]. Decorin accounts for ~40% of the total proteoglycan in the cornea [3]. Although decorins from various species and different tissues widely differ with respect to the overall proteoglycan structures due to variation in the structural features of their glycosaminoglycan (GAG) chains, all share 1570-9639/$ - see front matter D 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.bbapap.2004.06.007 Abbreviations: IRBCs, infected red blood cells; GAG, glycosamino- glycan; CS, chondroitin sulfate; PG, proteoglycan; CSPG, chondroitin sulfate proteoglycan; C4S, chondroitin 4-sulfate; DS, dermatan sulfate; DSPG, dermatan sulfate proteoglycan; BSA, bovine serum albumin; HexN, hexosamine; GalN, galactosamine; GlcN, glucosamine; PVDF, polyviny- ledene difluoride; DEAE, diethylaminoethyl; GdnHCl, guanidine hydro- chloride; NEM, N-ethylmaleimide; PBS, phosphate buffered saline; PMSF, phenylmethylsulfonyl fluoride; TLCK, N-a-tosyl-l-lysine chloromethyl ketone; TPCK, N-tosyl-l-phenylalanine chloromethyl ketone; PAGE, polyacrylamide gel electrophoresis; CAPS, 3-(cyclohexylamino)propane- sulfonic acid * Corresponding author. Tel.: +1 717 531 0992; fax: +1 717 531 7072. E-mail address: gowda@psu.edu (D. Channe Gowda). Biochimica et Biophysica Acta 1701 (2004) 109 – 119 www.bba-direct.com