Lymphocyte microvilli are dynamic, actin-dependent structures that do not require Wiskott-Aldrich syndrome protein (WASp) for their morphology.
Short microvilli cover the surfaces of circulating mammalian lymphocytes. The surfaces of monocytes and neutrophils are very different, containing ruffles as their predominant structure. In this study, we present the first quantitative characterization of lymphocyte microvilli. From analysis of scanning electron micrographs, we find that median microvillar length and surface density range from 0.3 to 0.4 microm and 2 to 4 microvilli/microm(2), respectively, on lymphocytes from a variety of sources. As with similar structures from other cells, lymphocyte microvilli contain parallel bundles of actin filaments. Lymphocyte microvilli rapidly disassemble when exposed to the actin-sequestering molecule, Latrunculin A. This disassembly parallels cellular actin filament depolymerization and is complete within 2 minutes, suggesting that lymphocyte microvilli undergo continuous assembly and disassembly. In contrast to previous reports suggesting lymphocyte microvillar density to be reduced on lymphocytes from Wiskott-Aldrich syndrome (WAS) patient, we find no such deficiency in either mouse or human WAS protein (WASp)-deficient lymphocytes. These results suggest that WASp is either not involved in or is redundant in the rapid dynamics of lymphocyte microvilli.
Majstoravich
Sonja
S
Department of Biochemistry HB7200, Dartmouth Medical School, Hanover, NH 03755-3844, USA.
Zhang
Jinyi
J
Nicholson-Dykstra
Susan
S
Linder
Stefan
S
Friedrich
Wilhelm
W
Siminovitch
Katherine A
KA
Higgs
Henry N
HN
D000199:Actins / Q000378:metabolism; D000818:Animals; D006801:Humans; D008214:Lymphocytes / Q000378:metabolism* / Q000648:ultrastructure*; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D008854:Microscopy, Electron; D008855:Microscopy, Electron, Scanning; D008871:Microvilli / Q000378:metabolism* / Q000648:ultrastructure; D011506:Proteins / Q000235:genetics / Q000378:metabolism*; D014923:Wiskott-Aldrich Syndrome / Q000378:metabolism* / Q000473:pathology; D051316:Wiskott-Aldrich Syndrome Protein
D000199:Actins; D011506:Proteins; C495767:WAS protein, human; C495768:Was protein, mouse; D051316:Wiskott-Aldrich Syndrome Protein