Interaction of the p62 subunit of dynactin with Arp1 and the cortical actin cytoskeleton.
Targeting of the minus-end directed microtubule motor cytoplasmic dynein to a wide array of intracellular substrates appears to be mediated by an accessory factor known as dynactin [1-4]. Dynactin is a multi-subunit complex that contains a short actin-related protein 1 (Arp 1) filament with capZ at the barbed end and p62 at the pointed end [5]. The location of the p62 subunit and the proposed role for dynactin as a multifunctional targeting complex raise the possibility of a dual role for p62 in dynein targeting and in Arp1 pointed-end capping. In order to gain further insight into the role of p62 in dynactin function, we have cloned cDNAs that encode two full-length isoforms of the protein from rat brain. We found that p62 is homologous to the nuclear migration protein Ropy-2 from Neurospora [6]; both proteins contain a zinc-binding motif that resembles the LIM domain of several other cytoskeletal proteins [7]. Overexpression of p62 in cultured mammalian cells revealed colocalization with cortical actin, stress fibers, and focal adhesion sites, sites of potential interaction between microtubules and the cell cortex [8,9]. The p62 protein also colocalized with polymers of overexpressed wild-type or barbed-end-mutant Arp1, but not with a pointed-end mutant. Deletion of the LIM domain abolished targeting of p62 to focal-adhesion sites but did not interfere with binding of p62 to actin or Arp1. These data implicate p62 in Arp1 pointed-end binding and suggest additional roles in linking dynein and dynactin to the cortical cytoskeleton.
Garces
J A
JA
Department of Cell Biology, University of Massachusetts Medical School, Worcester 01605, USA.
Clark
I B
IB
Meyer
D I
DI
Vallee
R B
RB
D000199:Actins / Q000378:metabolism*; D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D019556:COS Cells; D003001:Cloning, Molecular; D003599:Cytoskeleton / Q000378:metabolism*; D018076:DNA, Complementary / Q000235:genetics; D000072159:Dynactin Complex; D008840:Microfilament Proteins; D008869:Microtubule-Associated Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D008958:Models, Molecular; D009154:Mutation; D020033:Protein Isoforms / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D020836:Protein Structure, Quaternary; D051381:Rats; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D017384:Sequence Deletion; D016335:Zinc Fingers / Q000235:genetics; D018909:src Homology Domains
D000199:Actins; D018076:DNA, Complementary; C485513:Dbnl protein, rat; D000072159:Dynactin Complex; D008840:Microfilament Proteins; D008869:Microtubule-Associated Proteins; D020033:Protein Isoforms; D011994:Recombinant Proteins; C491475:actin-related protein 1, rat