Fibronectin isoforms in plasma membrane domains of normal and regenerating rat liver

Enrich, Carlos; Evans, William Howard; Gahmberg, Carl G.

doi:10.1016/0014-5793(88)80602-1

Cited by 16 publications

(10 citation statements)

References 25 publications

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“…During hepatic proliferation in development, regeneration, and oncogenesis, changes in hepatocyte polarity occur (42). Among adhesion molecules, fibronectin mRNA has several spliced forms which change in proliferative states of the liver (3,8,(33)(34)(35)(36)(37)47). During liver development, EIIIB exon-containing (EIIIB ϩ ) transcripts represent a significant percentage of fibronectin transcripts (37).…”

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confidence: 99%

HRS/SRp40-Mediated Inclusion of the Fibronectin EIIIB Exon, a Possible Cause of Increased EIIIB Expression in Proliferating Liver

Peng

Greenbaum

et al. 1997

Molecular and Cellular Biology

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Serine-arginine (SR)-rich proteins are believed to be important in mediating alternative pre-mRNA splicing. HRS/SRp40 expression is elevated in liver cell proliferation during development, regeneration, and oncogenesis. We tested whether HRS expression correlates with the appearance of alternatively spliced fibronectin transcripts during liver growth. HRS was highly expressed during the proliferative phase of liver development, correlating with expression of the fibronectin EIIIB alternative exon. In regenerating liver, HRS protein was induced in a time course consistent with the observed increase in fibronectin transcripts containing the EIIIB exon, particularly in nonparenchymal liver cells. Furthermore, in an in vivo assay, HRS, and not other SR proteins, directly mediated EIIIB exon inclusion in the fibronectin transcript. This alternative splicing was dependent on a purine-rich region within the EIIIB exon to which HRS specifically bound. We have established that HRS has the potential to contribute to the regulation of fibronectin pre-mRNA splicing during liver growth. Changes in fibronectin forms may be important in modifying liver architecture during the proliferative response, thus providing a potential mechanism by which SR proteins may participate in cellular growth control.The splicing factor HRS (hepatic arginine-serine protein) is expressed in proliferating liver cells. HRS is induced as an immediate-early gene in insulin-treated, mitogen-activated rat hepatoma H35 cells and in our study represented 12% of all insulin-induced cDNAs (7). HRS is a delayed-early gene in regenerating liver and is expressed at a very high level during liver development when the liver is rapidly proliferating (7, 46; reviewed in reference 9). HRS belongs to the serine-arginine (SR) protein family, which is comprised of at least nine structurally related proteins, including SRp20, SRp30a (SF2/ASF), SRp30b (SC35), SRp40, SRp55, and SRp75 (11,12,27,31,39,[52][53][54]. Comparing the partial sequence of human SRp40 and HRS sequence revealed that HRS is rat SRp40 (7, 52). Recently, the human homolog of HRS was identified and shown to have properties of other splicing factors in both in vitro and in vivo splicing assays (39).Pre-mRNA alternative splicing provides an important mechanism of gene and protein expression regulation (19,29,31,40). Through alternative splicing, one primary transcript can generate multiple proteins which may have different functions. Alternative splicing occurs via several pathways, including skipped exons, included introns, alternative 5Ј splice sites, alternative 3Ј splice sites, and mutually exclusive exons. SR proteins have been shown to play essential roles in both constitutive pre-mRNA splicing and regulation of pre-mRNA alternative splicing. In vitro and in vivo splicing assays indicate that SR proteins regulate alternative splicing by promoting the use of proximal 5Ј splice sites (10,23,26,55), and different SR proteins have distinct abilities to regulate alternative splicing of various model pr...

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confidence: 99%

HRS/SRp40-Mediated Inclusion of the Fibronectin EIIIB Exon, a Possible Cause of Increased EIIIB Expression in Proliferating Liver

Peng

Greenbaum

et al. 1997

Molecular and Cellular Biology

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“…In differentiated simple epithelia intercellular adhesive junctions are found on contiguous (lateral) surfaces and interactions with the extracellular matrix occur along the basal plasmalemma that faces the basement membrane (Simons and Fuller, 1985). The liver is unique among simple epithelia in thatfibronectin, a major extracellular matrix protein (Hynes, 1990) appears in nonpolarized fashion at apical (canalicular), lateral and basal (sinusoidal) cell surfaces, as distinct molecular forms Enrich et al, 1988), in contrast to other extracellular matrix components such as collagens, laminin, and proteoglycans which are exclusively located on sinusoidal cell sur-of ZO-1, a protein component of tight junctions. On the second day postpartum, presence of AGp110 and of protein constituents of desmosomes and intermediate junctions, DGI and E-cadherin, respectively, was notably enhanced in cellular fractions insoluble in nonionic detergents, presumably signifying linkage of AGp110 with the cytoskeleton and assembly of desmosomal and intermediate junctions .…”

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Temporal changes in the expression and distribution of adhesion molecules during liver development and regeneration.

Stamatoglou¹,

Enrich²,

Manson³

et al. 1992

The Journal of Cell Biology

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Abstract. We have compared by inimunocytochemistry and immunoblotting the expression and distribution of adhesion molecules participating in cell-matrix and cell-cell interactions during embryonic development and regeneration of rat liver. Fibronectin and the fibronectin receptor, integrin a5ß1, were distributed pericellularly and expressed at a steady level during development from the 16th day of gestation and in neonate and adult liver. AGp110, a nonintegrin fibronectin receptor was first detected on the 17th day of gestation in a similar, nonpolarized distribution on parenchymal cell surfaces. At that stage of development haemopoiesis is at a peak in rat liver and fibronectin and receptors a5ß1 and AGp110 were prominent on the surface of blood cell precursors. During the last 2 d of gestation (20th and 21st day) hepatocytes assembled around lumina . AGp110 was initially depolarized on the surface of these acinar cells but then confined to the lumen and to newly-formed bile canaliculi . At birth, a marked increase occurred in the canalicular expression of AGp110 and in the branching of the canalicular network. Simultaneously, there was enhanced expression C ELL adhesion is of fundamental importance in morphogenesis and cytodifferentiation, and particularly in the establishment and maintenance of cell polarization in epithelia (Edelman, 1986;Ekblom et al., 1986;Trelstad, 1984;Takeichi, 1991;Simons and Fuller, 1985;Wiley et al., 1990). In differentiated simple epithelia intercellular adhesive junctions are found on contiguous (lateral) surfaces and interactions with the extracellular matrix occur along the basal plasmalemma that faces the basement membrane (Simons and Fuller, 1985). The liver is unique among simple epithelia in thatfibronectin, a major extracellular matrix protein (Hynes, 1990) appears in nonpolarized fashion at apical (canalicular), lateral and basal (sinusoidal) cell surfaces, as distinct molecular forms Enrich et al., 1988), in contrast to other extracellular matrix components such as collagens, laminin, and proteoglycans which are exclusively located on sinusoidal cell sur-

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“…Although under the conditions adopted a high proportion of the membrane proteins were solubilized, the anomalous behaviour of some membrane and membrane-associated proteins, e.g. acetylcholine receptor subunits (Maher & Singer, 1985) and fibronectin isoforms in liver plasma membranes (Enrich et al, 1988), in two-phase partitioning systems has been reported. This tendency of categories of membrane proteins of intermediate hydrophobicity to partition anomalously is due in part to the presence of 0.7 mm-Triton X-1 14 in the aqueous phase (Pryde, 1986).…”

Section: Discussionmentioning

confidence: 99%

Priority targeting of glycosyl-phosphatidylinositol-anchored proteins to the bile-canalicular (apical) plasma membrane of hepatocytes. Involvement of ‘late’ endosomes

Ali¹,

Evans²

1990

Biochemical Journal

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1. Liver plasma membranes originating from the sinusoidal, lateral and canalicular surface domains of hepatocytes were covalently labelled with sulpho-N-hydroxysuccinamide-biotin. After solubilization in Triton X-114, treatment with a phosphatidylinositol-specific phospholipase C (PI-PLC), two-phase partitioning and 125I-streptavidin labelling of the proteins resolved by PAGE, six major polypeptides (molecular masses 110, 85, 70, 55, 38 and 35 kDa) were shown to be anchored in bile canalicular membrane vesicles by a glycosyl-phosphatidylinositol (G-PI) 'tail'. 2. Permeabilized 'early' and 'late' endocytic vesicles isolated from liver were also examined. Two polypeptides (110 and 35 kDa) were shown to be anchored by a G-PI tail in 'late' endocytic vesicles. 3. Analysis of marker enzymes in bile-canalicular vesicles treated with PI-PLC showed that 5'-nucleotidase and alkaline phosphatase, but not leucine aminopeptidase and ecto-Ca2(+)-ATPase activities were released from the membrane. A low release and recovery of alkaline phosphodiesterase activity was noted. The cleavage from the membrane of 5'-nucleotidase as a 70 kDa polypeptide was confirmed by Western blotting using an antibody to this enzyme. 4. Antibodies raised to proteins released from bile-canalicular vesicles by PI-PLC treatment, and purified by partitioning in aqueous and Triton X-114 phases, localized to the bile canaliculi in thin liver sections. Antibodies to proteins not hydrolysed by this treatment stained by immunofluorescence the sinusoidal and canalicular surface regions of hepatocytes. 5. Antibodies generated to proteins cleaved by PI-PLC treatment of canalicular vesicles were shown to identify, by Western blotting, a major 110 kDa polypeptide in these vesicles. Two polypeptides (55 and 38 kDa) were detected in MDCK and HepG-2 cultured cells. 6. Since two of the six G-PI-anchored proteins targeted to the bile-canalicular plasma membrane were also detected in 'late' endocytic vesicles, the results suggest that a junction where exocytic and endocytic traffic routes meet occurs in a 'late' endocytic compartment.

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Fibronectin isoforms in plasma membrane domains of normal and regenerating rat liver

Cited by 16 publications

References 25 publications

HRS/SRp40-Mediated Inclusion of the Fibronectin EIIIB Exon, a Possible Cause of Increased EIIIB Expression in Proliferating Liver

HRS/SRp40-Mediated Inclusion of the Fibronectin EIIIB Exon, a Possible Cause of Increased EIIIB Expression in Proliferating Liver

Temporal changes in the expression and distribution of adhesion molecules during liver development and regeneration.

Priority targeting of glycosyl-phosphatidylinositol-anchored proteins to the bile-canalicular (apical) plasma membrane of hepatocytes. Involvement of ‘late’ endosomes

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