Proteoglycans synthesized and secreted by pancreatic islet b-cells bind amylin Susan Potter-Perigo, a Rebecca L. Hull, b Christina Tsoi, a Kathleen R. Braun, a Sofianos Andrikopoulos, b Jeanette Teague, b C. Bruce Verchere, b Steven E. Kahn, b and Thomas N. Wight a,c, * a The Hope Heart Institute, Seattle, WA 98104, USA b VA Puget Sound Health Care System and Department of Medicine, Division of Metabolism, Endocrinology and Nutrition, University of Washington, Seattle, WA 98195, USA c Department of Pathology, School of Medicine, University of Washington, Seattle WA 98195, USA Received 11 December 2002, and in revised form 20 February 2003 Abstract Pancreatic islet amyloid deposits in type 2 diabetes are associated with decreased islet b-cell function. They contain both amylin (islet amyloid polypeptide), the b-cell-derived unique fibrillogenic component, and heparan sulfate proteoglycans (HSPGs). We hypothesized that b-cell HSPGs contribute to islet amyloidogenesis. [ 35 S]Sulfate-labeled proteoglycans from islet-derived b-TC3 cell cultures eluted from diethylaminoethyl Sephacel at 0.35M NaCl. Chromatography on Sepharose CL-4B and SDS–PAGE analysis revealed distinct populations of proteoglycans. Medium HSPGs eluted at K av  0:18 and 0.50 with glycosaminoglycan chains of 28 and 19kDa, respectively. A third population containing chondroitin/dermatan sulfate eluted at K av  0:70 with glycosami- noglycan chains of 10 kDa. A single size class of heparan and chondroitin/dermatan sulfate proteoglycans in the cell layer eluted at K av  0:40 with glycosaminoglycan chains of 19 kDa. Medium and cell layer proteoglycans bound exclusively to fibrillogenic amylin, as determined by gel mobility shift assays, indicating a possible role for b-cell-derived proteoglycans in islet amyloid for- mation. Ó 2003 Elsevier Science (USA). All rights reserved. Keywords: Proteoglycans; Amylin; Islet amyloid polypeptide; Type 2 diabetes; Islet amyloid; b-cells; Islet Islet amyloid is a pathologic feature of type 2 diabetes that occurs in the vast majority of subjects with the disease [1,2]. Islet amyloid deposits are associated with decreased b-cell mass and contribute to the progressive b-cell dysfunction seen in type 2 diabetes [3,4]. These deposits contain, as their unique component, amylin (islet amyloid polypeptide; IAPP) 1 , a normal secretory product of the b-cell that is coreleased with insulin [5–7]. The mechanisms underlying islet amyloid formation remain unclear but an amyloidogenic form of amylin, permitting a b-pleated sheet conformation, is required. Thus, islet amyloid develops in humans, nonhuman primates, and cats but not rodents, whose amylin is nonamyloidogenic [8]. However, production of an am- yloidogenic amylin molecule alone is not sufficient for amyloid formation to occur since islet amyloid is rarely seen in nondiabetic humans, even in the face of in- creased amylin secretion, as seen in obesity [2]. In addition to amylin, several other molecules are present in islet amyloid deposits, including heparan sulfate proteoglycans (HSPGs) [9–11]. A variety of dif- ferent proteoglycans have been found to be components of amyloid deposits in different tissues [9,10,12–17]. Proteoglycans are present on the surface of cells and in the extracellular matrix frequently as part of specialized structures such as basement membranes [9,10,12–17]. The exact role of proteoglycans in amyloid deposits is not entirely clear but a number of studies suggest that Archives of Biochemistry and Biophysics 413 (2003) 182–190 www.elsevier.com/locate/yabbi ABB * Corresponding author. Fax: 1-206-903-2088. E-mail address: twight@hopeheart.org (T.N. Wight). 1 Abbreviations used: IAPP, islet amyloid polypeptide; HSPGs, heparan sulfate proteoglycans; BSA, bovine serum albumin; CPC, cetylpryidinium chloride; DAEA, diethylaminoethyl. 0003-9861/03/$ - see front matter Ó 2003 Elsevier Science (USA). All rights reserved. doi:10.1016/S0003-9861(03)00116-4