title: Cellular uptake and subsequent intracellular trafficking of R8-liposomes introduced at low temperature.
abstract: Intracellular trafficking is a determining factor in the transgene expression efficiency of gene vectors. In the present study, the mechanism of the cellular uptake of octaarginine (R8)-modified liposomes, when introduced at 37 degrees C and 4 degrees C, was investigated in living cells. Compared with 37 degrees C, the uptake of R8-liposomes was only slightly reduced at 4 degrees C. Dual imaging of liposomes and plasma membranes revealed that R8-liposomes were internalized by vesicular transport, and partially escaped to the cytosol at the perinuclear region at 37 degrees C. When introduced at 4 degrees C, intracellular liposomes were observed within a specific region close to the plasma membrane, and internalization of the plasma membrane was completely inhibited. Therefore, at 4 degrees C, R8-liposomes appear to enter cells via unique pathway, which is separate and distinct from energy-dependent vesicular transport. The subsequent nuclear delivery of encapsulated pDNA, when introduced at 4 degrees C, was less prominent compared with those introduced at 37 degrees C. Collectively, these findings demonstrate that a vesicular transport-independent pathway is responsible for the cellular uptake of liposomes. In addition, the uptake route is closely related to the subsequent nuclear delivery process; the operation of an endogenous vesicular sorting system is advantageous for the nuclear delivery of pDNA.
authors.affiliation: Graduate School of Pharmaceutical Sciences, Hokkaido University, Sapporo, Hokkaido 060-0812, Japan.
authors.forename: Akitada
authors.initials: A
authors.lastname: Iwasa
authors.forename: Hidetaka
authors.initials: H
authors.lastname: Akita
authors.forename: Ikramy
authors.initials: I
authors.lastname: Khalil
authors.forename: Kentaro
authors.initials: K
authors.lastname: Kogure
authors.forename: Shiroh
authors.initials: S
authors.lastname: Futaki
authors.forename: Hideyoshi
authors.initials: H
authors.lastname: Harashima
mesh_terms: D001483:Base Sequence; D001692:Biological Transport; D003080:Cold Temperature; D017931:DNA Primers; D006358:Hot Temperature; D008081:Liposomes; D018613:Microscopy, Confocal; D019076:Transgenes
chemical_list: D017931:DNA Primers; D008081:Liposomes