TY - JOUR
T1 - A Dictyostelium myosin I plays a crucial role in regulating the frequency of pseudopods formed on the substratum
AU - Wessels, Deborah
AU - Titus, Margaret
AU - Soll, David R.
PY - 1996/1/1
Y1 - 1996/1/1
N2 - Analysis of the motile behavior of a strain of Dictyostelium lacking a myosin I, myoA, revealed that this mutant strain formed pseudopods and turned twice as frequently as wild type cells [Titus et al., 1993: Mol. Biol. Cell 4:233-246]. The basis for this aberrant behavior has been explored using three-dimensional reconstructions of translocating cells. Wild type cells form approximately 40% of pseudopods on the substratum and 60% off the substratum. The majority of pseudopods formed on the substratum initiate sharp turns while the majority of pseudopods formed off the substratum are retracted. Although myoA- cells form pseudopods at roughly twice the frequency of wild type cells, the increase in frequency is specific for only those pseudopods formed on the substratum. This increase is the basis for the aberrant increase in turning in myoA- cells. The selective increase in the frequency of pseudopods formed on the substratum correlates with a number of additional abnormalities in myoA- pseudopod formation. First, myoA- cells can simultaneously extend more than one pseudopod, whereas wild type cells extend only one pseudopod at a time. Second, although wild type and myoA- pseudopods achieve the same final volumes, myoA pseudopods grow at half the rate of wild type pseudopods and, therefore, take longer to achieve final volume. Third, while a wild type pseudopod grows in a continuous fashion, a myoA pseudopod grows in a discontinuous fashion. Together, these results demonstrate that myoA plays a fundamental role in controlling the frequency of only those pseudopods formed on the substratum, and that maintenance of the normal frequency of pseudopod formation appears to be necessary for the normal velocity of cellular translocation, the normal frequency of turning, the normal rate of average pseudopod growth, and the high efficiency of chemotaxis. These results in turn indicate that pseudopod formation is precisely coordinated in space and time, and actin-associated proteins like myoA play key roles in coordination.
AB - Analysis of the motile behavior of a strain of Dictyostelium lacking a myosin I, myoA, revealed that this mutant strain formed pseudopods and turned twice as frequently as wild type cells [Titus et al., 1993: Mol. Biol. Cell 4:233-246]. The basis for this aberrant behavior has been explored using three-dimensional reconstructions of translocating cells. Wild type cells form approximately 40% of pseudopods on the substratum and 60% off the substratum. The majority of pseudopods formed on the substratum initiate sharp turns while the majority of pseudopods formed off the substratum are retracted. Although myoA- cells form pseudopods at roughly twice the frequency of wild type cells, the increase in frequency is specific for only those pseudopods formed on the substratum. This increase is the basis for the aberrant increase in turning in myoA- cells. The selective increase in the frequency of pseudopods formed on the substratum correlates with a number of additional abnormalities in myoA- pseudopod formation. First, myoA- cells can simultaneously extend more than one pseudopod, whereas wild type cells extend only one pseudopod at a time. Second, although wild type and myoA- pseudopods achieve the same final volumes, myoA pseudopods grow at half the rate of wild type pseudopods and, therefore, take longer to achieve final volume. Third, while a wild type pseudopod grows in a continuous fashion, a myoA pseudopod grows in a discontinuous fashion. Together, these results demonstrate that myoA plays a fundamental role in controlling the frequency of only those pseudopods formed on the substratum, and that maintenance of the normal frequency of pseudopod formation appears to be necessary for the normal velocity of cellular translocation, the normal frequency of turning, the normal rate of average pseudopod growth, and the high efficiency of chemotaxis. These results in turn indicate that pseudopod formation is precisely coordinated in space and time, and actin-associated proteins like myoA play key roles in coordination.
KW - Dictyostelium discoideum
KW - MyoA mutant
KW - cell motility
KW - pseudopod formation
KW - three dimensional analysis
UR - http://www.scopus.com/inward/record.url?scp=0029586647&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=0029586647&partnerID=8YFLogxK
U2 - 10.1002/(SICI)1097-0169(1996)33:1<64::AID-CM7>3.0.CO;2-I
DO - 10.1002/(SICI)1097-0169(1996)33:1<64::AID-CM7>3.0.CO;2-I
M3 - Article
C2 - 8824735
SN - 0886-1544
VL - 33
SP - 64
EP - 79
JO - Cell Motility and the Cytoskeleton
JF - Cell Motility and the Cytoskeleton
IS - 1
ER -