Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P50583 (asymmetrical)
 12,197 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We describe the distribution of type II insulin-like growth factor receptors among canalicular (cLPM) and basolateral (bLPM) subfractions of rat liver plasma membranes (LPM). BLPM bound 3 times more 125I-IGF II than cLPM. The number of receptors was (1.3 +/- 0.15) X 10(-12) mol/mg in bLPM, and (0.4 +/- 0.17) X 10(-12) mol/mg in cLPM. Insulin-like growth factor II (IGF II) was 10 times more potent than insulin-like growth factor I (IGF I) in displacing 125I-IGF II from both basolateral and canalicular binding sites. Insulin did not interfere with binding of 125I-IGF II in either LPM preparations. Our findings point to an asymmetrical hepatocellular distribution of type II IGF receptors, thus extending the concept of surface polarization of hepatocytes to growth promoting hormone receptors.
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PMID:Polar surface distribution of type II insulin-like growth factor receptor in rat hepatocytes. 217 7

The syncytiotrophoblast, which is delineated by two polar membranes (the microvillous and the basal plasma membranes), is the main placental structural element controlling maternal-fetal exchanges. These studies of the full-term placenta were undertaken in order to determine whether the microvillous membranes, which are bathed by the maternal intervillous circulation, and basal plasma membrane, which lines the fetal blood capillaries, have binding sites for insulin-like growth factor (IGF)-II. The microvillous and basal plasma membranes were purified and found to bind 125I-IGF-II with significantly different (p < 0.0001) Kd (0.51 and 1.02 nM, respectively). There were more available binding sites in the microvillous (4.4+/-0.3 pmol/mg protein) than in the basal (2.7+/-0.4 pmol/mg protein) plasma membranes (p < 0.0001). Both membranes contained three major (250, 135, and 130 kDa) 125I-IGF-II/binding-site protein complexes as determined by affinity cross-linking and PAGE. The 250-kDa band (type 2 IGF receptor) was the main band in the basal plasma membranes (46% total bound 125I-IGF-II). The 135-kDa band (insulin-receptor alpha subunit) was the main one in the microvillous membranes (48% total bound 125I-IGF-II). The amounts of 130-kDa band (type 1 IGF-receptor alpha subunit) in the two types of membranes were similar (30% total bound 125I-IGF-II). Only IGF-II displaced 125I-IGF-II from the 250-kDa band, while 125I-IGF-II bound to the 135-kDa band was displaced by insulin, and ligand bound to the 130-kDa band was displaced by IGF-I. Thus there are IGF receptors in both types of membranes of syncytiotrophoblast in the human full-term placenta, and the distributions of the IGF and insulin receptors are asymmetrical. This may reflect the fact that they face and interact with two independent, different media. Maternal IGF may influence the syncytiotrophoblast by binding to receptors on the microvillous membranes, while fetal IGF may also influence syncytiotrophoblast functions by activating receptors in the basal plasma membranes.
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PMID:Differential distribution of binding sites for 125I-insulin-like growth factor II on trophoblast membranes of human term placenta. 947 20