生物谷 · 2011/12/02





Segregation of Protein Aggregates Involves Actin and the Polarity Machinery


Beidong Liu, Lisa Larsson, Vanessa Franssens, Xinxin Hao, Sandra Malmgren Hill, Veronica Andersson, Daniel Höglund, Jia Song, Xiaoxue Yang, David Öling , Julie Grantham, Joris Winderickx, Thomas Nyström

Cells of yeast to mammals have evolved the means of spatial quality control (SQC), which includes the transport of protein aggregates on microtubules into a structure called the aggresome (Kopito, 2000,Wang et al., 2009) and a factor-dependent compartmentalization of aggregates into juxtanuclear sites (JUNQ) and perivacuolar inclusions (IPOD) (Kaganovich et al., 2008). SQC also encompasses an actin cytoskeleton-, polarisome-, and Hsp104-dependent segregation of damaged proteins during yeast cytokinesis (Aguilaniu et al., 2003,Erjavec et al., 2007,Tessarz et al., 2009). In addition, some aggregates in yeast daughter cells were observed to move (retrograde) into the mother cell after a transient heat stress (Liu et al., 2010). In this issue of Cell, Zhou et al., 2011 now extend this analysis and, with the aid of theoretical simulations, suggest that motility of protein aggregates is characterized by random and slow diffusion, completely devoid of directional bias. Further, it is argued that aggregate asymmetry is established in a purely passive and random manner and that no active, factor-dependent (e.g., polarisome) mechanism is involved in conferring SQC. This model contrasts that of Tessarz et al., 2009 and Liu et al., 2010, which both interpret the failure of mutants with defects in polarisome and Hsp104 functions to establish damage asymmetry indicative of damage retention being a factor-dependent process.



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