In order to carry out their physiological functions, the cells of transporting epithelial tissues must be able to polarize their cell surface domains. Different collections of membrane transport proteins must be distributed to distinct domains of the plasma membrane, and cells must be coupled to one-another through junctional complexes that help organize polarized domains and regulate the permeability of the paracellular pathway. This exquisite organization requires that epithelial cells possess a sorting apparatus that can target newly synthesized transport proteins to the appropriate surface domains. Furthermore, the transport proteins themselves must possess information embedded within their structures that specifies their sites of ultimate functional residence. The nature of this information, and of the protein-protein interactions involved in its interpretation, is beginning to be elucidated. The initial formation of the polarized state involves signaling cascades that epithelial cells use to orient themselves to sites of cell-cell and cell-matrix contact. Recent evidence suggests that one component of these cascades is a kinase that also serves as a cellular energy sensor.
Animals ; Cell Polarity ; Epithelial Cells ; physiology ; Humans ; Membrane Transport Proteins ; physiology ; Protein Transport ; Signal Transduction

Vesicle-mediated transport of proteins is a highly regulated, multi-step process. When the vesicle is approaching its target membrane compartment, many factors are required to provide specificity and tethering between the incoming vesicle and the target membrane, before vesicle fusion can occur. Tethering factors, which include multisubunit complexes, coiled-coil proteins, with the help of small GTPases, provide the initial interaction between the vesicle and its target membrane. Of the multisubunit tethering factors, the transport protein particle (TRAPP) complexes function in a number of trafficking steps, including endoplasmic reticulum (ER)-to-Golgi transport, intra- and post-Golgi traffic and autophagosome formation. In this review, we summarize the updated progress in structure and function of TRAPP complexes as well as human diseases caused by genetic mutations in TRAPP.
Animals ; Endoplasmic Reticulum ; pathology ; physiology ; Golgi Apparatus ; pathology ; physiology ; Humans ; Mutation ; Protein Transport ; Vesicular Transport Proteins ; genetics ; physiology

The cystic fibrosis transmembrane conductance regulator (CFTR) is a unique member of the ATP-binding cassette (ABC) transporter superfamily that forms a Cl(-) channel with complex regulation. CFTR is composed of five domains: two membrane-spanning domains (MSDs), two nucleotide-binding domains (NBDs) and a unique regulatory domain (RD). The MSDs assemble to form a low conductance (6-10 pS) anion-selective pore with deep intracellular and shallow extracellular vestibules separated by a selectivity filter. The NBDs form a head-to-tail dimer with two ATP-binding sites (termed sites 1 and 2) located at the dimer interface. Anion flow through CFTR is gated by the interaction of ATP with sites 1 and 2 powering cycles of NBD dimer association and dissociation and hence, conformational changes in the MSDs that open and close the channel pore. The RD is an unstructured domain with multiple consensus phosphorylation sites, phosphorylation of which stimulates CFTR function by enhancing the interaction of ATP with the NBDs. Tight spatial and temporal control of CFTR activity is achieved by macromolecular signalling complexes in which scaffolding proteins colocalise CFTR and plasma membrane receptors with protein kinases and phosphatases. Moreover, a macromolecular complex composed of CFTR and metabolic enzymes (a CFTR metabolon) permits CFTR activity to be coupled tightly to metabolic pathways within cells so that CFTR inhibition conserves vital energy stores. CFTR is expressed in epithelial tissues throughout the body, lining ducts and tubes. It functions to control the quantity and composition of epithelial secretions by driving either the absorption or secretion of salt and water. Of note, in the respiratory airways CFTR plays an additional important role in host defence. Malfunction of CFTR disrupts transepithelial ion transport leading to a wide spectrum of human disease.
Cystic Fibrosis Transmembrane Conductance Regulator ; physiology ; Epithelium ; physiology ; Humans ; Ion Transport ; Phosphorylation ; Protein Interaction Domains and Motifs

To explore the effect of high fat diet on proteome in mice stomachs, we constructed a model in which the mice were fed with high fat diet as the high fat diet (HFD) group or normal diet as the control (CTRL) group for 110 days. The stomachs were collected and divided into three regions (forestomach (F), corpus (C) and antrum (A)) for protein extraction and mass spectrometry analysis. Of all 9 307 identified proteins in two groups, 4 066 proteins (HFD: 3 832, CTRL: 3 654) were strictly identified by at least one unique peptide and identified twice in three replicates. Using gene ontology (GO) and interaction network analysis we analyzed differentially expressed proteins (fold change≥2) in two groups or between regions. In the whole stomach tissues, proteins up-regulated in HFD group mainly were associated with protein stabilization and protein transport. Differentially expressed proteins between regions showed that forestomach was related to the biological process of keratinization and actin assembly, while corpus and antrum mainly performed digestive function. Compared with forestomach, the corpus and antrum were more affected by the diet. Though there was no significant effect on the basic digestive function of the stomach, proteins that were involved in protein transport and lipid metabolism-related biological processes were significantly highly expressed in HFD group.
Animals ; Diet, High-Fat ; Lipid Metabolism ; Mice ; Mice, Inbred C57BL ; Protein Transport ; Proteome ; physiology ; Stomach ; physiology

The delivery of bioactive macromolecular substances into cells provides an efficient approach to changing cellular conditions, and is thus of enormously potential therapeutic significance. It has also been an extremely difficult approach due the the impediment and protective nature of cell membrance until the protein transduction domain's (PTD's) capability to ferry macromolecule across cell membrance was discovered. PTD's efficient transductive function has rendered an exciting promise to the clinical treatment of diseases, therapeutic proteins drug development, and basic medical and applied research. The technology has been successfully applied to deliver a variety of substances into cells or tissue organs, and its superior application values have been explicitly demonstrated.
Cell Membrane Permeability ; physiology ; Drug Delivery Systems ; methods ; Genetic Therapy ; Humans ; Protein Sorting Signals ; Protein Transport ; physiology

Time-dependent translocational changes of Synapsin I (SyI), a synaptic vesicle-associated phosphoprotein and its involvement in the axonal transport were investigated in the regenerating axonal sprouts. A weak SyI immunoreactivity (IR) was found in the axoplasm of normal axons. Rat sciatic nerves were crush-injured by ligating with 1-0 silk thread at the mid-thigh level and released from the ligation 24 h later. At various times after release, immunocytochemistry was performed. SyI was translocated from the proximal to the distal site of ligation and also involved in the sprouting of regenerating axons. The distribution patterns of SyI IR were changed in the crush-injured nerves. SyI immunoreactive thin processes were strongly appeared in the proximal region from 1 h after release. After 3 h, a very strong IR was expressed. The intense SyI immunoreactive thin processes were elongated distally and were changed the distribution pattern by time-lapse. After 12 h, strong immunoreactive processes were extended to the ligation crush site. At 1 day, a very intense IR was expressed. At 2 days, immunoreactive thin processes extended into the distal region over the ligation crush site and strong IR was observed after 3 days. SyI was accumulated in the proximal region at the early phases after release. These results suggest that SyI may be related to the translocation of vesicles to the elongated membranes by a fast axonal transport in the regenerating sprouts.
Animals ; Axonal Transport ; Axons/*physiology/ultrastructure ; Immunohistochemistry ; Male ; Nerve Crush ; Nerve Regeneration/*physiology ; Protein Transport ; Rats ; Rats, Sprague-Dawley ; Sciatic Nerve/physiology ; Synapsins/*metabolism ; Time Factors

Active Transport, Cell Nucleus ; physiology ; Animals ; Cell Nucleus ; physiology ; Cilia ; physiology ; Humans ; Molecular Motor Proteins ; physiology ; beta Karyopherins ; physiology ; ran GTP-Binding Protein ; physiology

Protein transport from endoplasmic reticulum (ER) to Golgi apparatus has long been known to be a central process for protein quality control and sorting. Recent studies have revealed that a large number of signal molecules are involved in regulation of membrane trafficking through ER, ER-Golgi intermediate compartment and Golgi apparatus. These molecules can significantly change the transport rate of proteins by regulating vesicle budding and fusion. Protein transport from ER to Golgi apparatus is not only controlled by signal pathways triggered from outside the cell, it is also regulated by feedback signals from the transport pathway.
Endoplasmic Reticulum ; metabolism ; Golgi Apparatus ; metabolism ; Humans ; Protein Transport ; physiology ; Secretory Pathway ; Signal Transduction

This study examined the radiation-induced ERBB2 nuclear transport in the BT474 breast cancer cell line and the relationship between caveolin-1 and radiation-induced ERBB2 nuclear transport. The BT474 cells were treated with herceptin (200 nmol/L), PP2 (a caveolin-1 inhibitor, 100 nmol/L) and irradiation combined or alone. Confocal microscopy was used to observe the nuclear import of ERBB2 and caveolin-1 after irradiation. Western blotting was employed to detect the expression of ERBB2, caveolin-1 and DNA-PKcs after irradiation, and immunoprecipitation to identify the ERBB2 and caveolin-1 complex before perinuclear ERBB2 localization. Confocal microscopy showed the transport of ERBB2 and caveolin-1 from the cell membrane to the nucleus 15 min after irradiation and the proteins accumulated at the perinuclear region within 45 min. Western blotting revealed that the expression levels of ERBB2, caveolin-1 and DNA-PKcs were increased after irradiation and reached a peak 45 min later. Both herceptin and PP2 treatments were found to decrease ERBB2 expression. An immune complex composed of ERBB2 and caveolin-1 was found in the herceptin group after irradiation. It was concluded that after irradiation, ERBB2 may be transported from the cell membrane to the nucleus and activate DNA-PKcs to trigger DNA double-strand break (DSB) repair; caveolin-1 may participate in this process. Treatments involving the downregulation of caveolin-1 may increase the radiosensitization of breast cancer cells.
Active Transport, Cell Nucleus ; physiology ; Breast Neoplasms ; metabolism ; physiopathology ; Caveolin 1 ; metabolism ; Cell Line, Tumor ; Female ; Humans ; Protein Transport ; physiology ; Radiation ; Receptor, ErbB-2 ; metabolism

Inhibin, which is important for normal gonadal function, acts on the pituitary gonadotropins to suppress folliclestimulating hormone (FSH) secretion. The level and cellular localization of the inhibin isotypes, alpha, beta(A) and beta(B), in the testis of mice were examined during postnatal development in order to determine if inhibin expression is related to testicular maturation. Mouse testes were sampled on postnatal days (PNDs) 1, 3, 6, 18, 48 and 120, and analyzed by Western blotting and immunofluorescence. Western blot analysis showed very low levels of inhibin alpha, beta(A) and beta(B) expression in the testes at days 1 to 6 after birth. The levels then increased gradually from PND 18 to 48-120, and there were significant peaks at PND 48. Inhibin alpha, beta(A) and beta(B) were detected in testicular cells during postnatal development using immunohistochemistry. The immunoreactivity of inhibin alpha was rarely observed in testicular cells during PND 1 to 6, or in the cytoplasmic process of Sertoli cells surrounding the germ cells and interstitial cells during PND 18 to 120. Inhibin beta(A) and beta(B) immunoreactivity was rarely observed in the testis from PND 1 to 6. On the other hand, it was observed in some spermatogonial cells, as well as in the interstitial space between PND 48 and PND 120. We conclude that the expression of inhibin isotypes increases progressively in the testis of mice with increasing postnatal age, suggesting that inhibin is associated with a negative feedback signal for FSH in testicular maturation.
Aging/*physiology ; Animals ; Gene Expression Regulation/*physiology ; Inhibin-beta Subunits/genetics/*metabolism ; Inhibins/genetics/*metabolism ; Male ; Mice ; Mice, Inbred ICR ; Protein Isoforms/metabolism ; Protein Transport/*physiology ; Testis/*metabolism