The present results also confirm the previous studies describing co-aggregate formation of wild type and CTF TDP-43.[32, 38] Similar results Navitoclax supplier were also obtained when we infected the cells with adenoviruses encoding mutant TDP-43 instead of wild type TDP-43; we failed to observe any differences in effects between wild type and mutant TDP-43 expressing
adenoviruses to induce aggregate formation. The toxic effect of the mutation in TDP-43 gene remains elusive, as several reports also failed to demonstrate enhancing effects by the mutation to form aggregates in cultured cells.[8, 35-37] As for aggregate formation by FUS transgenes in transfected cells in vitro, it has been described that FUS point mutations showed a varying degree of cytoplasmic accumulation, ranging from mild (R521C, R521G), intermediate (R522G) to
severe (P525L) mislocalization.[40, Ruxolitinib mouse 41] The degree of cytoplasmic mislocalization was inversely correlated to the age of disease onset.[40, 41] In line with these observations, we demonstrated that adenovirus-induced FUS with R521C or R521G mutation was localized both in the nucleus and cytoplasm with granular appearance, and FUS with R522G or P525L mutation was localized predominantly in the cytoplasm forming larger aggregates. Furthermore, like TDP-43 adenoviruses, aggregate formation was enhanced when the cells were infected with the mutated FUS adenoviruses in the presence of MG-132 or 3MA, or in combination with PSMC1, ATG5 or VPS24 shRNA adenovirus infection (Table 1). The relationship between cytoplasmic aggregates of TDP-43
and FUS proteins and stress granules has been extensively studied.[40-44] Although whether Coproporphyrinogen III oxidase cytoplasmic aggregates demonstrated in the present study also related to stress granules awaits further investigation, it is noteworthy that inhibition of the proteasome activity by MG-132 induces the formation of stress granules in HeLa cells, suggesting that the present treatments of MG-132 or PSMC1 shRNA adenovirus also induced stress granules and subsequent aggregate formation in neuronal and glial cells. In the present study, we demonstrated retrograde transport of facial nerve-injected adenoviruses encoding TDP-43, FUS and shRNAs for protein degradation pathways to the rat facial motoneurons and expression of the virus-induced foreign genes in these motoneurons. In a similar manner to the present in vitro experiments as described above, facial motoneurons showed cytoplasmic aggregate formation when infected with adenoviruses encoding wild type and CTF TDP-43 and shRNAs for proteasome, autophagy, or endosome, or mutated FUS with these shRNAs, indicating that impairment of protein degradation pathways also greatly accelerates formation of TDP-43 and FUS-positive aggregates in adult rat facial motoneurons in vivo.