Regulation of raft-derived endocytic pathways : studies on echovirus 1 and baculovirus

Elina Kakkonen tutki väitöskirjassaan kahden erilaisen viruksen, echovirus 1:n ja bakuloviruksen soluun sisäänmenon reittejä ja säätelijöitä. Echovirus 1 (EV1) on ihmisiä infektoiva pikornavirus, joka voi aiheuttaa esimerkiksi aivokalvontulehdusta, sydänlihastulehdusta sekä lievempiä hengitystieinfektioita. Bakulovirus puolestaan on ihmisille vaaraton, hyönteisiä infektoiva virus, joka on osoittautunut lupaavaksi geeninsiirtokuljettajaksi geeniterapiassa.Virukset voivat käyttää soluun tunkeutumisessaan hyväkseen soluissa valmiina olevia erilaisia reittejä, joita solut itse tarvitsevat esimerkiksi ravintoaineiden sisäänottoon. Näin virukset pääsevät solun sisälle solun oman koneiston kuljett…

The closure of Pak1-dependent macropinosomes requires the phosphorylation of CtBP1/BARS

Membrane fission is an essential process in membrane trafficking and other cellular functions. While many fissioning and trafficking steps are mediated by the large GTPase dynamin, some fission events are dynamin independent and involve C-terminal-binding protein-1/brefeldinA-ADP ribosylated substrate (CtBP1/BARS). To gain an insight into the molecular mechanisms of CtBP1/BARS in fission, we have studied the role of this protein in macropinocytosis, a dynamin-independent endocytic pathway that can be synchronously activated by growth factors. Here, we show that upon activation of the epidermal growth factor receptor, CtBP1/BARS is (a) translocated to the macropinocytic cup and its surroundi…

Clathrin-independent entry of baculovirus triggers uptake of E. coli in non-phagocytic human cells

The prototype baculovirus, Autographa californica multiple nucleopolyhedrovirus, an insect pathogen, holds great potential as a gene therapy vector. To develop transductional targeting and gene delivery by baculovirus, we focused on characterizing the nature and regulation of its uptake in human cancer cells. Baculovirus entered the cells along fluid-phase markers from the raft areas into smooth-surfaced vesicles devoid of clathrin. Notably, regulators associated with macropinocytosis, namely EIPA, Pak1, Rab34, and Rac1, had no significant effect on viral transduction, and the virus did not induce fluid-phase uptake. The internalization and nuclear uptake was, however, affected by mutants o…

CtBP3/BARS-proteiinin merkitys echovirus 1:n ja α2β1-integriinin internalisaatiossa

A Raft-derived, Pak1-regulated Entry Participates in α2β1 Integrin-dependent Sorting to Caveosomes

We have previously shown that a human picornavirus echovirus 1 (EV1) is transported to caveosomes during 2 h together with its receptor alpha2beta1 integrin. Here, we show that the majority of early uptake does not occur through caveolae. alpha2beta1 integrin, clustered by antibodies or by EV1 binding, is initially internalized from lipid rafts into tubulovesicular structures. These vesicles accumulate fluid-phase markers but do not initially colocalize with caveolin-1 or internalized simian virus 40 (SV40). Furthermore, the internalized endosomes do not contain glycosylphosphatidylinositol (GPI)-anchored proteins or flotillin 1, suggesting that clustered alpha2beta1 integrin does not enter…