Isoforms of amino acid transporters in placental syncytiotrophoblast: plasma membrane localization and potential role in maternal/fetal transport.

Many cell proteins exist as isoforms arising either from gene duplication or alternate RNA splicing. There is growing evidence that isoforms with different, but closely related, functional characteristics are often directed to discrete cellular locations. Thus, specialized functions may be carried out by proteins of similar evolutionary origin in different membrane compartments.

Lysine uptake by cloned hCAT-2B: comparison with hCAT-1 and with trophoblast surface membranes.

To study the cationic amino-acid transporter hCAT-2B of human placenta, total RNA was harvested from primary cultured trophoblast and from the BeWo choriocarcinoma cell line (b30 clone) and used for reverse transcription (RT) and polymerase chain reaction (PCR). Primers based on published sequences identified expression of mRNA for hCAT-2B. RT-PCR yielded a 2.

Stable polarized expression of hCAT-1 in an epithelial cell line.

Our laboratory has recently identified and cloned three cationic amino-acid transporters of human placenta. We have now examined the plasma membrane domain localization and functional expression of one of these transporters, hCAT-1, in a polarized epithelial cell line (MDCK). To facilitate identification of expressed protein we first transferred the hCAT-1 cDNA to a vector with C-terminal green fluorescent protein (GFP).

Biophysical and biological properties of naturally occurring high molecular weight insulin-like growth factor II variants.

A soluble form of the insulin-like growth factor II/mannose 6-phosphate receptor (sIGF-II/MPR) is present in fetal bovine serum and carries mature 7.5-kDa insulin-like growth factor II (IGF-II) and at least 12 different high molecular weight (Mr) IGF-II isoforms (Valenzano, K. J.

Increased low density lipoprotein receptor expression mediated through the insulin-like growth factor-I receptor in cultured fibroblasts.

Plasma insulin-like growth factor-I (IGF-I) levels are inversely correlated with apolipoprotein B and low density lipoprotein (LDL) cholesterol in humans. To identify a molecular basis for this observation, the effects of IGF-I on LDL receptor expression in fibroblasts were studied. IGF-I increased LDL receptors in cultured human skin fibroblasts at concentrations greater than 25 ng/ml.