MDCK cells secrete neutral proteases cleaving insulin-like growth factor-binding protein-2 to -6

Liliana Shalamanova; Bernd Kübler; Jens-Gerd Scharf; Thomas Braulke

$Abstract Proteolysis of insulin-like growth factor-binding proteins (IGFBPs) may be an important mechanism to regulate IGF availability and IGF-independent functions of IGFBPs. We analyzed the secretion of IGFBP proteases in Madin-Darby canine kidney (MDCK) cells. The results showed that several specific proteases were secreted, cleaving IGFBP-2 to -6 at neutral pH. The proteolytic activity against IGFBP-6 differed at least from IGFBP-5 protease activity in its sensitivity both to IGF-II and to the hydroxamic acid-based disintegrin metalloprotease inhibitor, as well as serine protease inhibitors. During partial purification steps, the serine protease inhibitor-sensitive fraction with IGFBP-6 protease activity was separated from fractions characterized by the presence of a 30-kDa disintegrin immunoreactive band. Whereas the IGFBP-4 and -6 proteases are predominantly secreted across the basolateral membrane, the majority of IGFBPs are sorted to the apical medium from filter-grown cells. These studies indicate that the side-specific secretion of several distinct IGFBP proteases with partially overlapping IGFBP specificities may be another level in the regulation of IGF-dependent epithelial functions. insulin-like growth factor-binding proteins and proteases polarized sorting disintegrin metalloprotease Footnotes Address for reprint requests and other correspondence: T. Braulke, Univ. of Hamburg, Children's Hospital—Biochemistry, Martinistr. 52, D-20246 Hamburg, Germany (E-mail: braulke@uke.uni-hamburg.de ). The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked “ advertisement ” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact. Copyright © 2001 the American Physiological Society$

MDCK cells secrete neutral proteases cleaving insulin-like growth factor-binding protein-2 to -6

Shalamanova, Liliana; Kübler, Bernd; Scharf, Jens-Gerd; Braulke, Thomas

Follow AJP - Endocrinology and Metabolism , Volume 281 (6): E1221 The American Physiological Society – Dec 1, 2001