Overproduction of perlecan core protein in cultured cells and transgenic mice

Abstract

Heparan sulphate proteoglycan (HSPG) and amyloid P component are the only macromolecules consistently associated with all varieties of amyloid, irrespective of the type of amyloid protein, suggesting that HSPG may play a pathogenetic role in amyloid formation through a common mechanism. In the case of Alzheimer's disease (AD), HSPG, such as perlecan, co-accumulates with amyloid-beta protein (Abeta), a main constituent of amyloid plaques, and paired helical filaments (PHFs). Additionally, in vitro, HSPG accelerates both Abeta fibril and PHF formation and protects Abeta from degradation. Therefore, this study first established lines of P19 mouse embryonic carcinoma cells stably carrying an expression vector encoding the complete perlecan core protein (approximately 400 kD). In the cell lysates, overexpressed perlecan was identified as an approximately 400 kD protein without glycosaminoglycan side-chains, while in the media, secreted perlecan was mostly glycosylated, suggesting that the secretion and glycosylation of perlecan are coupled. Next, transgenic mice were produced using the same expression vector. Marked perlecan overexpression occurred in the cytoplasm of multiple tissues including the brain, heart, kidney, and pancreas, without a discernible increase of perlecan in extracellular matrices. The transgenic mice up to 18 months of age did not develop amyloid or AD-like pathology in the brain or elsewhere, based on histochemical and immunohistochemical analyses. Thus, overproduction of perlecan core protein is insufficient to lead to amyloidosis and AD-like pathology.

Heparan sulfate proteoglycan induces the production of NO and TNF-α by murine microglia

“…Most of these effects of HSPG have been shown to be due to its associated HSGAG side-chains, as also suggested by the lack of extracellular Aβ deposits in transgenic mice overexpressing HSPG protein core [47]. This contrasts with our results showing that the proinflammatory role of HSPG is primarily mediated by its protein core.…”

Multifunctionality of extracellular and cell surface heparan sulfate proteoglycans

“…In contrast to loss-of-function studies, over-expression of Pln core protein in multiple tissues including brain and heart did not result in obvious developmental defects [81]. Recently, knock-in mouse models for the non-lethal autosomal recessive Schwartz-Jampel type I syndrome (SJS, MIM 255800) in which reduced amounts of perlecan protein are expressed have been created [82,83].…”

Cellular Response of Cardiac Fibroblasts to Amyloidogenic Light Chains

“…Recently, a transgenic mouse was made where perlecan was overexpressed to study its effect on HSPGs in the development of amyloidosis. 45 Surprisingly, while both intracellular accumulation and extracellular deposition were present, there was no increase in amyloidosis. 46 These results raise additional questions concerning the underlying mechanisms.…”