Extracellular phosphorylation converts pigment epithelium-derived factor from a neurotrophic to an antiangiogenic factor.

The pigment epithelium-derived factor (PEDF) belongs to the superfamily of serine protease inhibitors (serpin). There have been 2 distinct functions attributed to this factor, which can act either as a neurotrophic or as an antiangiogenic factor. Besides its localization in the eye, PEDF was recently reported to be present also in human plasma.

Distal hinge of plasminogen activator inhibitor-1 involves its latency transition and specificities toward serine proteases.

Background: The plasminogen activator inhibitor-1 (PAI-1) spontaneously converts from an inhibitory into a latent form. Specificity of PAI-1 is mainly determined by its reactive site (Arg346-Met347), which interacts with serine residue of tissue-type plasminogen activator (tPA) with concomitant formation of SDS-stable complex. Other sites may also play roles in determining the specificity of PAI-1 toward serine proteases.

Secretion of pigment epithelium-derived factor. Mutagenic study.

Pigment epithelium-derived factor (PEDF), a neurotrophic and antiangiogenic protein, is an extracellular component of the retinal interphotoreceptor matrix which has been shown to be secreted by human fetal retinal pigment epithelial cells. It belongs to the serpin superfamily and contains the typical exposed reactive center loop. The function of this loop is still unknown.

A selective interaction between OS-9 and the carboxyl-terminal tail of meprin beta.

OS-9, a protein previously uncharacterized, was shown to interact specifically with the intracellular region of the membrane proteinase meprin beta found in brush border membranes of kidney and small intestine. We have shown previously that this cytoplasmic region is indispensable for the maturation of meprin beta, which included an endoplasmic reticulum (ER)-to-Golgi translocation. We characterized OS-9 and found that it is associated with ER membranes and that it is exposed to the cytoplasm.

YOS9, the putative yeast homolog of a gene amplified in osteosarcomas, is involved in the endoplasmic reticulum (ER)-Golgi transport of GPI-anchored proteins.

The OS-9 gene maps to a region (q13-15) of chromosome 12 that is highly amplified in human osteosarcomas and encodes a protein of unknown function. Here we have characterized a homolog designated as YOS9 (YDR057w) from Saccharomyces cerevisiae. The yeast protein (Yos9) is a membrane-associated glycoprotein that localizes to the endoplasmic reticulum (ER).