Endosomal integrity

Cationic lipids and polymers (including dendrimers) deliver DNA and siRNA into cells via cargo compaction to give lipoplexes or polyplexes (or dendriplexes), respectively, of various sizes which are then taken up via non-specific endocytosis (see Fig. 1). Once these complexes have been endocytosed the cargo has to be released into the cytoplasm to avoid degradation by the lysosomes. This escape is based upon the ability of the carrier to dismpt endosomal integrity [29-33] and is a critical step in the process. Once in the cytoplasm, the genetic material needs to be... 

Shin, H., Morinaga, N., Masatoshi, N., and Nakayama, K. (2004). BIG2, a guanine nucleotide exchange factor for ADP-ribosylation factors Its localization to recycling endosomes and implication in the endosome integrity. Mol. Biol. Cell 15, 5283-5294. 

The HR Vs must undergo a number of transitions to replicate (Figure 3). First, they must attach to the cell surface at a cellular receptor. They are then internalized into the cell via the endosomal compartment. Following internalization, they must eject their RNA out of the viral capsid, through a lipid bilayer, and into the cytosol in a manner that preserves the integrity of the RNA. Replication... 

Figure 12.1 Cellular barriers to gene delivery. Extracellular DNA, delivered to cells in either viral particles, liposomes, or other vehicles, must traverse the plasma, endosomal, and nuclear membranes before any transcription, replication, or integration can occur.

By means of PCI enhanced siRNA delivery was shown for the first time by Oliveira et al. They demonstrated a tenfold increased knockdown efficiency of the EGF receptor due to improved endosomal release by the activated PS meso-tetra-phenylporphine, which was, however, not integrated in the polyplex [155]. 

Fig. 6.2. Model for how FcRn rescues IgG from catabolism by recycling and transcytosis. IgG and many other soluble proteins are present in extracellular fluids. Vascular endothelial cells are active in fluid phase endocytosis of blood proteins. Material taken up by these cells enters the endosomes where FcRn is found as an integral membrane protein. The IgG then binds FcRn in this acidic environment. This binding results in transport of the IgG to the apical plasma membrane for recycling into the circulation, or to the basolateral membrane for transcytosis into the extracellular space. Exposure to a neutral pFI in both locations then results in the release of IgG. The remaining soluble proteins are channeled to the lysosomal degradation pathway.

The genome in influenza A and B types is enclosed within an outer lipoprotein envelope (Fig. 17.1). The Ml protein lines the inside of the envelope and is chemically bound to the ribonucleoprotein [14], The Ml protein plays an important role in the mediation of nuclear export of viral ribonucleoproteins and also in virus assembly and budding during the infectious cycle [5, 14, 15], An antigenic protein M2, which functions as a proton-selective ion channel, is present in the viral membrane of influenza A viruses [6, 13], In influenza B, the ion channel activity to aid virus uncoating in the endosome is carried out by the similar integral membrane protein BM2 [11],... 

Their proximity is established in neuroendocrine and neuronal cells, where BLOC-1 and AP-3 have been found on the same population of synaptophysin-containing vesicles (Salazar et al., 2005b, 2006). Synaptophysin is an integral membrane protein of SVLMs in PC-12 cells and of synaptic vesicles derived either from presynaptic membranes by AP-2 or from endosomes by AP-3 (cf. Salazar et al., 2004b, 2005b and Takamori et al., 2006). 

S(mem), S(end/lys), S(cyt) and S(nuc), respectively. These parameters represent the total amount of pDNA in each compartment in the whole cell. Furthermore, the total area of the pDNA denoted as S(tot) was calculated by integrating the S(mem), S(end/lys), S(cyt) and S(nuc). This value represents the total cellular association of pDNA. The fractions of pDNA present on the plasma membrane, endosomes/lysosomes, cytosol and nucleus to the whole cell are denoted as F(mem), F(end/lys),... 

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