Matthew Welch: The many branches of actin regulation

T he actin cytoskeleton powers a variety of processes, from cell migration to intracellular membrane transport. Pathogens often harness their host's actin network to their own ends, hijacking the cytoskeleton to drive cell entry, survival, and intercellular spread. Matthew Welch studies the many different mechanisms that host cells and pathogens use to initiate actin fi lament assembly at the right time and place. Welch fi rst became interested in actin as a graduate student with David Drubin at the University of California, Berkeley, where he used genetics to look for actin-interacting proteins in yeast (1). During his postdoc with Tim Mitchison at the University of California, San Francisco, Welch identifi ed the Arp2/3 complex as the host factor that nucleates branched actin assembly on the surface of invasive Listeria to power bacterial movement through the cytoplasm (2) and found that the same complex is present in lamellipodia (3). Since his return to Berkeley to start his own laboratory, Welch has continued to work on the Arp2/3 complex (4) and the various nucleation-promoting factors that stimulate Arp2/3 activity at different locations within the cell (5, 6). He's also continued to study how pathogens subvert actin dynamics, recently demonstrating that Rickettsia species express a formin-like protein to nucleate unbranched actin fi laments which drive bacterial locomo-tion (7) and that certain viruses also can move with the help of their host's actin cytoskeleton (8). In a recent interview, we asked Welch what fi rst nucleated his interest in actin and where his research interests are propelling him next. Where did you grow up? I grew up in a town called Mt. Kisco in Westchester County, New York. My parents still live there. My father was a statistician who worked for IBM at the Thomas J. Watson Research Center. I used to go into work with him and although he didn't work in a laboratory himself—he was more involved in the computing side of things— there were several laboratories in the building. So I kind of grew up around science. In high school I was interested primarily in chemistry because I had a really good teacher. But I also liked biology and physics. How did you fi rst get interested in actin? I didn't know anything about actin or the cytoskeleton until I got to Berkeley for grad school. I'd been a molecular and cell biology major at the University of Michigan, but I'd …