Calcium/Calmodulin-Dependent Protein Kinase Kinase 2 Regulates Macrophage-Mediated Inflammatory Responses (172.35)

Abstract

Calcium/calmodulin-dependent Kinase Kinase 2 (CaMKK2) plays a key role in regulating food intake and energy expenditure at least in part by its actions in hypothalamic neurons. Previously we showed that loss of CaMKK2 protected mice from high fat diet (HFD)-induced obesity and glucose intolerance. However, whereas pair-feeding HFD to WT mice to match food consumption of CAMKK2-null mice slowed weight gain, it failed to protect from glucose intolerance. Here we show that relative to WT mice, HFD-fed CaMKK2-null mice are protected from inflammation in adipose and remain glucose tolerant. Moreover, loss of CaMKK2 also protected mice from endotoxin shock and fulminant hepatitis. We explored the expression of CaMKK2 in immune cells, and found it to be restricted to those of the monocyte/macrophage lineage. CaMKK2-null macrophages exhibited a remarkable deficiency to spread, phagocytize bacteria and synthesize cytokines in response to the Toll Like Receptor 4 (TLR4) agonist lipopolysaccharide (LPS). Mechanistically, loss of CaMKK2 uncoupled the TLR4 cascade from activation of protein tyrosine kinase 2 (PYK2; also known as PTK2B). Our findings uncover an important function for CaMKK2 in mediating mechanisms that control the amplitude of macrophage inflammatory responses to excess nutrients or pathogen derivatives.