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This Article Full Text Full Text (PDF) Data Supplement All Versions of this Article: jimmunol.0803301v1 183/6/4021    most recent Alert me when this article is cited Alert me if a correction is posted Citation Map Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Request Permissions Google Scholar Articles by Martin, U. Articles by Gabel, C. A. PubMed PubMed Citation Articles by Martin, U. Articles by Gabel, C. A.

Externalization of the Leaderless Cytokine IL-1F6 Occurs in Response to Lipopolysaccharide/ATP Activation of Transduced Bone Marrow Macrophages

Unja Martin^*, John Scholler, Jesse Gurgel, Blair Renshaw^*, John E. Sims^* and Christopher A. Gabel^1,*

^* Department of Inflammation and Department of Oncology, Amgen, Seattle, WA 98119

An interesting trait shared by many members of the IL-1 cytokine family is the absence of a signal sequence that can direct the newly synthesized polypeptides to the endoplasmic reticulum. As a result, these cytokines accumulate intracellularly. Recent studies investigating IL-1β export established that its release is facilitated via activation of an intracellular multiprotein complex termed the inflammasome. The purpose of the current study was to explore the mechanism by which murine IL-1F6 is released from bone marrow-derived macrophages (BMDMs) and to compare this mechanism to that used by IL-1β. BMDMs were engineered to overexpress IL-1F6 by retroviral transduction; cells overexpressing GFP also were generated to provide a noncytokine comparator. The transduced cells constitutively expressed IL-1F6 and GFP, but they did not constitutively release these polypeptides to the medium. Enhanced release of IL-1F6 was achieved by treating with LPS followed by ATP-induced activation of the P2X₇ receptor; GFP also was released under these conditions. No obvious proteolytic cleavage of IL-1F6 was noted following P2X₇ receptor-induced release. Stimulus-induced release of IL-1F6 and GFP demonstrated comparable susceptibility to pharmacological modulation. Therefore, transduced IL-1F6 is released in parallel with endogenous mature IL-1β from LPS/ATP-treated BMDMs, but this externalization process is not selective for cytokines as a noncytokine (GFP) shows similar behavior. These findings suggest that IL-1F6 can be externalized via a stimulus-coupled mechanism comparable to that used by IL-1β, and they provide additional insight into the complex cellular processes controlling posttranslational processing of the IL-1 cytokine family.

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 Address correspondence and reprint requests to Dr. Chris A. Gabel, Inflammation Department, Amgen, 1201 Amgen Court West, Mailstop 2262, Seattle, WA 98119-3105. E-mail address: gabel{at}amgen.com

² Abbreviations used in this paper: BMDM, bone marrow-derived macrophage; fph, flag-poly-his; CM, conditioned medium.

³ The online version of this article contains supplementary material.