Termination of lung inflammation by MYD88 alternative splicing

The National Institutes of Health National Heart, Lung, and Blood Institute awarded National Jewish Health $1,559,468 on July 10, 2026, under the Cardiovascular Diseases Research program (CFDA 93.837) to investigate the physiological function of MyD88 alternative splicing in terminating lung inflammation.

The research examines how alternative pre-mRNA splicing of the MyD88 gene regulates toll-like receptor signaling and inflammatory response. The project focuses on two MyD88 splice forms: the long form (MyD88-L), which mediates pro-inflammatory signaling through NF-κB and AP-1 activation, and the alternative short form (MyD88-S), which acts as a dominant-negative inhibitor. Prior studies manipulated MyD88-S levels only in cell lines; this award funds the first in vivo investigation using a novel mouse line lacking MyD88-S. The research will determine the mechanism by which MyD88-S differentially inhibits NF-κB while activating AP-1 during inflammation, and will assess how this differential effect impacts pro-inflammatory gene expression and lung inflammation pathology.

The award is structured as a Project Grant, the standard assistance type for individual research investigations. Performance occurs in Denver, Colorado, at National Jewish Health's facilities. The period of performance runs from the award date through June 30, 2028.

Abstract

In the presence of pathogens, the toll-like receptor (TLR) signaling pathway induces inflammation to fight infection. However, persistent TLR signaling can contribute to lung inflammatory disorders. One mechanism that regulates the persistence of TLR signaling is alternative pre-mrna splicing. For example, the MYD88 gene can produce two different mrna splice forms. The long form (MYD88-l) encodes the canonical signaling adaptor that mediates the response to multiple tlrs and that activates the transcription factors NFb and AP- 1 to drive pro-inflammatory gene expression. In contrast, the alternative short splice form MYD88-s encodes a protein that is a dominant negative inhibitor of NFb activation. Production of MYD88-s is induced by pathogens, so MYD88 alternative splicing is theorized to serve as a negative feedback loop to terminate TLR signaling and prevent chronic inflammatory disease. However, this hypothesis has never been tested. All prior studies on MYD88-s function have been performed in cell lines, not in vivo. Moreover, while MYD88-s levels have been experimentally manipulated, MYD88-s has never been knocked out. To determine the physiological function of MYD88-s, we generated a novel mouse line that lacks MYD88-s. Based on our preliminary studies with mice lacking MYD88-s, we hypothesize that, contrary to the dogma that MYD88-s is a simple inhibitor of inflammation, MYD88-s acts as a switch protein that inhibits NFb but activates AP-1 during inflammation. We will test this hypothesis by: (1) determining the mechanism used by MYD88-s to inhibit NFb but activate AP-1 and (2) determining how this differential effect of MYD88-s impacts pro-inflammatory gene expression and lung inflammation.