LSP1, but not other actin-binding proteins, is expressed at varied levels in stably transfected, monocyte-differentiated U937 cell lines.

Shown in (A) are immunoblots with anti-LSP1 monoclonal antibody and in (B) the relative LSP1 levels in human monocytes (lane 7) and a variety of stably transfected U937 cell lines (lane 1-6). Quantitative analyses were performed on immunoblot by scanning densitometry. Results are expressed relative to monocytes. Lanes 1, 3, and 5 are U937 cell lines with negative, lower, and higher LSP1 expression, respectively. Lane 1 is the control U937 cell transfected with pCEP4 vector only. The cell lines used in the locomotion study are db-cAMP–treated above cell lines indicated as MI-U937⁻ (lane 2), MI-U937⁺ (lane 4), and MI-U937⁺⁺⁺⁺ (lane 6), respectively. (C) Antifilamin, anti–α-actinin, antigelsolin, and antitropomyosin immunoblots of MI-U937⁻, MI-U937⁺, and MI-U937⁺⁺⁺⁺ cells. In each lane, 50 μg of total cellular proteins from these cells were loaded. Filamin, gelsolin, α-actinin, and tropomyosin are expressed at equivalent levels in stably transfected monocyte-differentiated U937 cell lines. (D) F-actin quantitative analysis performed on these MI cell lines by flow cytometry of the cells stained with NBD-phallacidin. Results are expressed relative to MI-U937⁻ cells (lane 2) as mean ± SD (n = 4-5).