Serine phosphate, threonine phosphate and γ-carboxyglutamic acid in normal and experimentally induced, pathologically calcified rat skin (topical cutaneous calciphylaxis)

Abstract

The amount of non-collagenous proteins is increased greatly during the pathological calcification of rat skin experimentally induced by dihydrotachysterol (DHT) and Ovalbumin (topical cutaneous calciphylaxis). This is accompanied by an increase in the total amount and concentrations of protein-bound serine phosphate [Ser(P)], threonine phosphate [Thr(P)] and gamma-carboxyglutamic acid (Gla), almost all of which can be extracted from the tissue and can be dissociated from collagen in 0.5M EDTA. The EDTA-soluble, non-collagenous proteins are rich in aspartic and glutamic acids, similar to the non-collagenous, EDTA-soluble proteins of bone, cementum and calcified cartilage, and quite distinct from those of dentin and enamel.

The Hormonal and Local Regulation of Bone Formation*

“…In addition to Winter, 1983 BONE FORMATION 73 osteonectin and osteocalcin, bone contains other noncollagenous proteins, although they have not been completely characterized. Bone matrix contains phosphoproteins which increase during local and ectopic calcification (189,190) and a bone morphogenetic protein which induces the local development and calcification of bone in extraskeletal tissues (191,192). These proteins may regulate mineralization but their effect on bone formation has not been examined.…”

Calcergy and calciphylaxis: Timed appearance of γ-carboxyglutamic acid and osteocalcin in mineral deposits

“…Gla-containing proteins have been identified in many examples of ectopic calcification and ossification including kidney stones [I1], hardened atherosclerotic plaque [10,12], calcified heart valves [13], artificial blood pump concretions [23], subcutaneous lesions associated with dermatomyositis and scleroderma [10], and in calciphylaxis [24]. The mechanism by which calcium phosphate deposits in either normal or pathologically mineralized tissues is incompletely understood.…”