INTERACTION BETWEEN MITOCHONDRIA AND THE ACTIN CYTOSKELETON IN BUDDING YEAST REQUIRES 2 INTEGRAL MITOCHONDRIAL OUTER-MEMBRANE PROTEINS, MMM1P AND MDM10P
I. Boldogh et al., INTERACTION BETWEEN MITOCHONDRIA AND THE ACTIN CYTOSKELETON IN BUDDING YEAST REQUIRES 2 INTEGRAL MITOCHONDRIAL OUTER-MEMBRANE PROTEINS, MMM1P AND MDM10P, The Journal of cell biology, 141(6), 1998, pp. 1371-1381
Transfer of mitochondria to daughter cells during yeast cell division
is essential for viable progeny. The actin cytoskeleton is required fo
r this process, potentially as a track to direct mitochondrial movemen
t into the bud. Sedimentation assays reveal two different components r
equired for mitochondria-actin interactions: (I) mitochondrial actin b
inding protein(s) (mABP), a peripheral mitochondrial outer membrane pr
otein(s) with ATP-sensitive actin binding activity, and (2) a salt-ine
xtractable, presumably integral, membrane protein(s) required for dock
ing of mABP on the organelle. mABP activity is abolished by treatment
of mitochondria with high salt. Addition of either the salt-extracted
mitochondrial peripheral membrane proteins (SE), or a protein fraction
with ATP-sensitive actin-binding activity isolated from SE, to salt-w
ashed mitochondria restores this activity. mABP docking activity is sa
turable, resistant to high salt, and inhibited by pretreatment of salt
-washed mitochondria with papain. Two integral mitochondrial outer mem
brane proteins, Mmm1p (Burgess, S.M., M. Delannoy, and R.E. Jensen. 19
94, J. Cell Biol. 126:1375-1391) and Mdm10p, (Sogo,,F,, and M.P. Yaffe
. 1994. J. Cell Biol. 126:1361-1373) are required for these actin-mito
chondria interactions. Mitochondria isolated from an mmm1-1 temperatur
e-sensitive mutant or from an mmm10 deletion mutant show no mABP activ
ity and no mABP docking activity. Consistent with this, mitochondrial
motility in vivo in mmm1-1 and mdm10 Delta mutants appears to be actin
independent. Depolymerization of F-actin using latrunculin-A results
in loss of long-distance, linear movement and a fivefold decrease in t
he velocity of mitochondrial movement. Mitochondrial motility in mmm1-
1 and mdm10 Delta mutants is indistinguishable from that in latrunculi
n-A-treated wild-type cells. We propose that Mmm1p and Mdm10p are requ
ired for docking of mABP on the surface of yeast mitochondria and coup
ling the organelle to the actin cytoskeleton.