Mucin, a major protein component in mucus, plays a critical role in mucosal innate defense by providing a
physical barrier and trapping pathogens for mucociliary clearance. If uncontrolled, excessive mucin production
overwhelms mucociliary clearance and causes conductive hearing loss in otitis media (OM) and mucus
obstruction in lung infections. Therefore, mucin production must be tightly regulated. However, the molecular
mechanisms underlying the tight regulation of mucin remain largely unknown.
Otitis media (OM) is the most common childhood bacterial infection and the leading cause of conductive
hearing loss. It remains a major health problem and a substantial socioeconomic burden. S. pneumoniae, Sp,
represents a major gram-positive bacterial pathogen for OM. Currently available Sp vaccines have a limited
impact on OM. Moreover, inappropriate antibiotic use increased antibiotic-resistance. There is an urgent need
for developing innovative non-antibiotic therapeutic agent for suppressing mucus overproduction. Our long-term
goal is to elucidate the molecular mechanisms underlying OM pathogenesis and identify novel therapeutic
targets. In contrast to the relatively well-known toll-like receptor (TLR)-dependent mechanisms by which Sp and
pneumolysin (PLY – a key virulence factor produced by virtually all clinical Sp isolates) induce host mucosal
immune response, the TLR-independent mechanisms including the key regulators remain largely unclear.
Adenosine 5’-monophosphate-activated protein kinase a1 (AMPKa1) has emerged as a master regulator of host
energy homeostasis. Its role in infectious diseases, in particular in the host mucosal innate defense response,
e.g. mucus production, remains largely unclear. Our encouraging preliminary data suggest that Sp and PLY may
up-regulate mucin MUC5AC and MUC5B via activation of AMPKa1 in a TLR2/4-independent manner in the
middle ear and airway epithelial cells in vitro and in the mouse models of both acute and chronic OM.
Interestingly, Sp and PLY may activate AMPKa1 by inducing novel non-traditional (protein degradation-
independent) ubiquitination of AMPKa1 likely via downregulating a key deubiquitinase CYLD. Together, these
exciting preliminary data have thus provided a solid foundation for us to hypothesize that  AMPKa1 acts as a
key regulator for Sp-induced up-regulation of MUC5AC and MUC5B via TLR-independent signaling; 
Activation of AMPKa1 by interplay between polyubiquitination and phosphorylation plays a critical role in Sp-
induced up-regulation of MUC5AC and MUC5B (hypothesis). To test our hypothesis, we will pursue two specific
aims to determine (Aim 1) the role of AMPKa1 in OM pathogenesis in both AOM and COM; and (Aim 2) how
Sp activates AMPKa1. These studies will significantly advance our understanding of the key regulators including
AMPK in TLR-independent host mucosal innate defense in bacterial infections and lead to the identification of
novel therapeutic targets for controlling mucus overproduction. Our AMPK signaling studies may also help
understand molecular mechanisms of other AMPK-related diseases (Significance and Impact).