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A Role for Connexin43 in Macrophage Phagocytosis and Host Survival after Bacterial Peritoneal Infection¹

Rahul J. Anand^2,*,, Shipan Dai^2,*,, Steven C. Gribar^*,, Ward Richardson^*,, Jeff W. Kohler^*,, Rosemary A. Hoffman, Maria F. Branca^*,, Jun Li^*,, Xiao-Hua Shi^*,, Chhinder P. Sodhi^*, and David J. Hackam^3,*,

^* Division of Pediatric Surgery, Children’s Hospital of Pittsburgh, and University of Pittsburgh School of Medicine, Pittsburgh, PA 15213; and Department of Surgery, University of Pittsburgh School of Medicine, Pittsburgh, PA, 15213

The pathways that lead to the internalization of pathogens via phagocytosis remain incompletely understood. We now demonstrate a previously unrecognized role for the gap junction protein connexin43 (Cx43) in the regulation of phagocytosis by macrophages and in the host response to bacterial infection of the peritoneal cavity. Primary and cultured macrophages were found to express Cx43, which localized to the phagosome upon the internalization of IgG-opsonized particles. The inhibition of Cx43 using small interfering RNA or by obtaining macrophages from Cx43 heterozygous or knockout mice resulted in significantly impaired phagocytosis, while transfection of Cx43 into Fc-receptor expressing HeLa cells, which do not express endogenous Cx43, conferred the ability of these cells to undergo phagocytosis. Infection of macrophages with adenoviruses expressing wild-type Cx43 restored phagocytic ability in macrophages from Cx43 heterozygous or deficient mice, while infection with viruses that expressed mutant Cx43 had no effect. In understanding the mechanisms involved, Cx43 was required for RhoA-dependent actin cup formation under adherent particles, and transfection with constitutively active RhoA restored a phagocytic phenotype after Cx43 inactivation. Remarkably, mortality was significantly increased in a mouse model of bacterial peritonitis after Cx43 inhibition and in Cx43 heterozygous mice compared with untreated and wild-type counterparts. These findings reveal a novel role for Cx43 in the regulation of phagocytosis and rearrangement of the F-actin cytoskeleton, and they implicate Cx43 in the regulation of the host response to microbial infection.

The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked advertisement in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.

¹ This work was supported by National Institutes of Health Grant RO1 GM078238-01 (to D.J.H.), the Resident Research Award from the Surgical Infection Society (to R.J.A.), and from the American College of Surgeons (to S.C.G.), as well as a Loan Repayment Award from the National Institutes of Health (to S.C.G.).

² R.J.A. and S.D. contributed equally to this work.

³ Address correspondence and reprint requests to Dr. David J. Hackam, Children’s Hospital of Pittsburgh, 3705 Fifth Avenue, 4A485 DeSoto Wing, Pittsburgh, PA 15213. E-mail Address: david.hackam{at}chp.edu

⁴ Abbreviations used in this paper: Cx43, connexin43; DIC, differential interference contrast; dn, dominant negative; LAMP-2, lysosomal-associated membrane protein 2; LPA, lysophasphatidic acid; siRNA, small interfering RNA; SRBC, sheep RBC; wt, wild type.