Integrin engagement regulates monocyte differentiation through the forkhead transcription factor Foxp1
Can Shi, … , Mukesh K. Jain, Daniel I. Simon
Can Shi, … , Mukesh K. Jain, Daniel I. Simon
Published August 1, 2004
Citation Information: J Clin Invest. 2004;114(3):408-418. https://doi.org/10.1172/JCI21100.
View: Text | PDF
Article Vascular biology

Integrin engagement regulates monocyte differentiation through the forkhead transcription factor Foxp1

Abstract

The precise signals responsible for differentiation of blood-borne monocytes into tissue macrophages are incompletely defined. “Outside-in” signaling by integrins has been implicated in modulation of gene expression that affects cellular differentiation. Herein, using differential display PCR, we have cloned an 85-kDa forkhead transcription factor (termed Mac-1–regulated forkhead [MFH] and found subsequently to be identical to Foxp1) that is downregulated in β2-integrin Mac-1–clustered compared with Mac-1–nonclustered monocytic THP-1 cells. MFH/Foxp1 is expressed in untreated HL60 cells, and its expression was markedly reduced during phorbol ester–induced monocyte differentiation, but not retinoic acid–induced granulocyte differentiation. Overexpression of MFH/Foxp1 markedly attenuated phorbol ester–induced expression of c-fms, which encodes the M-CSF receptor and is obligatory for macrophage differentiation. This was accompanied by decreased CD11b expression, cell adhesiveness, and phagocytosis. Using electromobility shift and reporter assays, we have established that MFH/Foxp1 binds to previously uncharacterized sites within the c-fms promoter and functions as a transcriptional repressor. Deficiency of Mac-1 is associated with altered regulation of MFH/Foxp1 and monocyte maturation in vivo. Taken together, these observations suggest that Mac-1 engagement orchestrates monocyte-differentiation signals by regulating the expression of the forkhead transcription repressor MFH/Foxp1. This represents a new pathway for integrin-dependent modulation of gene expression and control of cellular differentiation.

Authors

Can Shi, Xiaobin Zhang, Zhiping Chen, Karina Sulaiman, Mark W. Feinberg, Christie M. Ballantyne, Mukesh K. Jain, Daniel I. Simon

×

Figure 6

Options: View larger image (or click on image) Download as PowerPoint
Effect of full-length MFH/Foxp1 and amino- and carboxy-terminal deletion...
Effect of full-length MFH/Foxp1 and amino- and carboxy-terminal deletion mutants on c-fms promoter activity. (A) Activity of the c-fms promoter. To map the repression domain of MFH/Foxp1, a series of NH2- and COOH-terminal MFH/Foxp1 deletion mutants were generated. Deletion mutants were designed on the basis of the predicted modular domain structure of MFH/Foxp1 in order to establish the contribution of the glutamine-rich (Q-rich, amino acids 55–200), zinc-finger (Zn-finger, amino acids 308–331), and winged-helix/forkhead DNA-binding (amino acids 465–536) regions to the repressor activity of MFH/Foxp1. NIH 3T3 cells were transfected with 0.5 μg c-fms reporter gene plasmid, 0.05 μg pCMV-β-gal, and expression plasmids (5.5 μg) for pcDNA3.1 (vector), full-length MFH/Foxp1, or deletion mutants added to each well of a 12-well plate. Luciferase activities were determined, normalized on the basis of β-galactosidase activity, and plotted as percent promoter activity compared with that induced by treatment with vector alone. Triplicate determination of three to five independent experiments (mean ± SD) is shown. *P < 0.01. (B) Verification of MFH/Foxp1 mutant expression. Western blot analysis of NIH 3T3 lysates verifies expression of MFH/Foxp1 and NH2- and COOH-terminal MFH/Foxp1 deletion mutants: vector alone (lane 1), full-length MFH/Foxp1 amino acids 1–677 (lane 2), 430–677 (lane 3), 224–677 (lane 4), 1–222 (lane 5), and 1–428 (lane 6).