Abstract. Adsorptive-mediated transcytosis (AMT) provides a means for brain delivery of medicines across the blood-brain barrier (BBB). The BBB is readily equipped for the AMT process: it provides both the potential for binding and uptake of cationic molecules to the luminal surface of endothelial cells, and then for exocytosis at the abluminal surface. The transcytotic pathways present at the BBB and its morphological and enzymatic properties provide the means for movement of the molecules through the endothelial cytoplasm. AMT-based drug delivery to the brain was performed using cationic proteins and cell-penetrating peptides (CPPs). Protein cationization using either synthetic or natural polyamines is discussed and some examples of diamine/polyamine modified proteins that cross BBB are described. Two main families of CPPs belonging to the Tat-derived peptides and Syn-B vectors have been extensively used in CPP vector-mediated strategies allowing delivery of a large variety of small molecules as well as proteins across cell membranes in vitro and the BBB in vivo. CPP strategy suffers from several limitations such as toxicity and immunogenicity-like the cationization strategy-as well as the instability of peptide vectors in biological media. The review concludes by stressing the need to improve the understanding of AMT mechanisms at BBB and the effectiveness of cationized proteins and CPP-vectorized proteins as neurotherapeutics.

FSH receptor is selectively expressed on the surface of the blood vessels of a wide range of tumors. (Funded by INSERM.).

The complementary DNA for human thyroid-stimulating hormone (TSH) receptor encodes a single protein with a deduced molecular mass of 84.5 kDa. This protein is cleaved during its maturation in the human thyroid since the receptor protein has been shown to be composed of two subunits (a subunit of = 53 kDa and p subunit of = 38 kDa) held together by disulfide bridges [Loosfelt, H., Pichon, C., Jolivet, A., Misrahi, M., Caillou, B., Jamous, M., Vannier, B. & Milgrom, E. (1992) Proc. Nutl Acad. Sci. USA 89, 3765-37691. A similar processing occurs in an L cell line permanently expressing the human TSH receptor. The processing is however incomplete, resulting in a permanent accumulation of a 95-kDa high-mannose precursor which is present only in trace amounts in the thyroid. Pulse-chase experiments show the successive appearance in the L cells of two precursors: initially the = 95-kDa high-mannose glycoprotein followed by a = 120-kDa species containing mature oligosaccharides. This latter precursor is then processed into the a and p subunits. In primary cultures of human thyrocytes precursors of similar size are detected.Spodopteru frugiperda insect cells (Sf9 and Sf21) infected with a recombinant baculovirus encoding the human TSH receptor synthesize a monomeric protein of about 90 kDa soluble only in denaturing conditions. Comparison with the product of in vitro transcription-translation experiments (= 80 m a ) , suggests that it may be incompletely or improperly glycosylated. The TSH receptor expressed in these cells is unable to bind the hormone.Immunoelectron microscopy studies show that in human thyrocytes most of the receptor is present on the cell surface; in L cells the receptor is detected on the cell surface, as well as in the endoplasmic reticulum and in the Golgi apparatus (this intracellular pool of receptor molecules probably corresponding to the high-mannose precursor) ; in insect cells nearly all the receptor molecules are trapped in the endoplasmic reticulum. These differences in receptor distribution are concordant with the differences observed for receptor processing.The thyroid-stimulating hormone (TSH) receptor has been the subject of extensive studies (reviews in [l, 21). Interest in this receptor stems not only from its key role in the control of thyroid function and growth (review in [3]), but also from its direct implication in autoimmune diseases. Autoantibodies against the TSH receptor display either a stimulatory effect and mimic the action of the hormone, provoking Graves' disease, or a blocking effect and lead to idiopathic myxoedema (reviews in [l, 2, 4, 51). However, due to its fragility and scarcity, attempts to purify the TSH receptor have been unsuccessful. Conflicting results have been reCorrespondence to E. Milgrom, HBpital de BicCtre, 3kme niveau, F-94275 Kremlin-Bicstre, FranceAbbreviations. TSH, thyroid stimulating hormone ; TSHR, thyroid stimulating hormone receptor; Sf, Spodopteru frugiperdu insect cells ; AcMNPV, Autogrupha Culifornicu multiple nuclear polyhedrosis virus ; D...

Scant information is available to date on the intracellular trafficking of the TSH receptor. In the present study we have used stably transfected L cells that express the TSH receptor, 225I-labeled TSH, and antireceptor antibodies as well as gold-conjugated antireceptor monoclonal antibodies and hormone. The latter allowed us to study, by electron microscopy, the cellular distribution and endocytosis of TSH receptor. The receptor was initially localized on the plasmalemma proper and in clathrin-coated pits but was excluded from smooth vesicles open to the cell surface. It was internalized through clathrin-coated vesicles. Constitutive endocytosis represented 10% of cell surface receptor molecules. Endocytosis was increased 3-fold by incubation with hormone. The majority of internalized receptor molecules (90%) was recycled to the cell surface, whereas the hormone was degraded in lysosomes. This recycling of receptor was inhibited by administration of monensin. Electron microscopic and confocal microscopic studies were repeated in primary cultures of human thyroid cells and showed a distribution, and endocytosis pathways, very similar to those observed in transfected L cells. A previous study has shown the LH receptor to be endocytosed in high proportion and to be degraded in lysosomes. Confocal microscopy and colocalization studies with transferrin receptor confirmed that the highly homologous LH and TSH receptors exhibit, when expressed in the same cells, very different cellular trafficking properties. The use of LH/TSH receptor chimeras showed that transmembrane-intracellular domains contain information orienting the protein toward recycling or degradative pathways. The extracellular domain seems to play a role in the extent of intemalization. These observations should now allow the identification of the molecular signals involved.

Abstract. Monoclonal anti-receptor antibodies were used to study the cellular traffic of the hCG/LH receptor by immunoelectron microscopy. The LHR38 antibody was shown to bind to the extraceUular domain of the receptor but not to interfere with hormone binding, adenylate cyclase activation or with the rate of internalization of the receptor. Pig Leydig cells and a permanent L-cell line expressing the LH receptor were used for the study. Incubation with LHR38-gold complexes showed the LH receptors to be randomly distributed over the cell surface including the clathrin coated pits. The LH receptors were internalized via a route including coated pits, coated vesicles and multivesicular bodies to lysosomes. This route is different from that observed for/3-adrenergic, muscarinic, and yeast mating factor receptors and considered previously as possibly general for G-protein-coupled receptors. The use of [~25I]LHR38 allowed precise measurement of the rate of internalization, showing the existence of a constitutive pathway which was increased 11-fold by hormone administration. Double labeling experiments suggested that the hormone (hCG-Au~sm) and the receptor (labeled with LHR38-Ausm) have similar routes of endocytosis, both of them being degraded in lysosomes. Studies of the reappearance of LHR38-Aus~ on the surface of the cells and the use of monensin indicated that only a very small proportion of the receptor molecules were recycled to the cell surface. The distribution and the intracellular pathways of LH receptors are very similar in Leydig cells and transfected L-cells. This opens the possibility of using the latter to study, by in vitro mutagenesis, the molecular mechanisms involved in the cellular traffic of LH receptors. C ELL surface receptors for various ligands differ in their localization and their mechanisms and pathways of internalization. These receptors may be: (a) either specifically included in the coated pits (i.e., LDL-receptors [3,4], transferrin receptors [18][19][20]); (b) expressed only outside the coated pits on the membrane (i.e., B-adrenergic receptors) (37); or (c) randomly exposed on the cell surface, coated pits included (i.e., EGF-receptors) (11,12). Under the effect of the ligand (or sometimes constitutively) (16, 46) the receptor is internalized and may follow one of the four major endocytic pathways which have been described: (a) the ligand-receptor complex dissociates at the endosomal level; the receptor is recycled to the surface whereas the ligand is degraded in lysosomes (i.e., LDL receptor) (7); (b) the ligand-receptor complex is recycled to the cell surface, dissociates and the receptor is reused (i.e., transferrin receptor) (20); (c) the ligand-receptor complex is delivered by transcytosis to the opposite front of polarized cells where the ligand is released intact and the receptor partlally degraded (i.e., IgA receptor) (31); and (d) both partners are transported to lysosomes and degraded (i.e., EGFreceptor) (12).The hCG/LH receptor is involved in the regulation of steroidogenes...

BackgroundThe Follicle Stimulating Hormone receptor (FSHR) is expressed by the vascular endothelium in a wide range of human tumors. It was not determined however if FSHR is present in metastases which are responsible for the terminal illness.MethodsWe used immunohistochemistry based on a highly FSHR-specific monoclonal antibody to detect FSHR in cancer metastases from 6 major tumor types (lung, breast, prostate, colon, kidney, and leiomyosarcoma ) to 6 frequent locations (bone, liver, lymph node, brain, lung, and pleura) of 209 patients.ResultsIn 166 patients examined (79%), FSHR was expressed by blood vessels associated with metastatic tissue. FSHR-positive vessels were present in the interior of the tumors and some few millimeters outside, in the normally appearing tissue. In the interior of the metastases, the density of the FSHR-positive vessels was constant up to 7 mm, the maximum depth available in the analyzed sections. No significant differences were noticed between the density of FSHR-positive vessels inside vs. outside tumors for metastases from lung, breast, colon, and kidney cancers. In contrast, for prostate cancer metastases, the density of FSHR-positive vessels was about 3-fold higher at the exterior of the tumor compared to the interior. Among brain metastases, the density of FSHR-positive vessels was highest in lung and kidney cancer, and lowest in prostate and colon cancer. In metastases of breast cancer to the lung pleura, the percentage of blood vessels expressing FSHR was positively correlated with the progesterone receptor level, but not with either HER-2 or estrogen receptors. In normal tissues corresponding to the host organs for the analyzed metastases, obtained from patients not known to have cancer, FSHR staining was absent, with the exception of approx. 1% of the vessels in non tumoral temporal lobe epilepsy samples.ConclusionFSHR is expressed by the endothelium of blood vessels in the majority of metastatic tumors.

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We observed four families with loss of function mutations of the TSH receptor gene. One patient had a homozygous Pro162 Ala substitution. The three other were compound heterozygotes: 1) Gln324-->Stop and Asp410 Asn2), Cys41 Ser and Phe525 Leu, 3) Cys390 Trp and Trp546-->Stop. In all patients, the plasma TSH concentration was increased, whereas T3 and T4 concentrations were normal. The TSH levels were normal in the heterozygous parents. These results confirmed the recessive character of TSH receptor defects. Expression of the various mutated receptors in transfected COS-7 cells demonstrated the impairment of their function. We studied the expression of the receptors on the cell surface by immunofluorescence, their ability to bind hormone, and their capacity to activate adenylate cyclase. Some mutations allowed us to identify sites that are especially important for receptor function. The substitution Cys390 Trp abolished high affinity hormone binding. Receptor mutated at Asp410 Asn bound the hormone normally, but failed to activate adenylate cyclase. This result underscores the role of this acidic extracellular residue, close to the first transmembrane segment, in signal transmission. The Phe525 Leu substitution also markedly impaired adenylate cyclase activation, underlining the importance of the second intracellular loop in receptor signaling.