Citations

To investigate the cellular dynamics of ZAP-70, we have studied the distribution and regulation of its intracellular location using a ZAP-70 green fluorescent protein chimera. Initial experiments in epithelial cells indicated that ZAP-70 is diffusely located throughout the quiescent cell, and accumulates at the plasma membrane upon cellular activation, a phenotype enhanced by the coexpression of Lck and the initiation of ZAP-70 kinase activity. Subsequent studies in T cells confirmed this phenotype. Intriguingly, a large amount of ZAP-70, both chimeric and endogenous, resides in the nucleus of quiescent and activated cells. Nuclear ZAP-70 becomes tyrosine phosphorylated upon stimulation via the T cell receptor, indicating that it may have an important biologic function.

Transduction of energetic signals into membrane electrical events governs vital cellular functions, ranging from hormone secretion and cytoprotection to appetite control and hair growth. Central to the regulation of such diverse cellular processes are the metabolism sensing ATP-sensitive K + (K ATP ) channels. However, the mechanism that communicates metabolic signals and integrates cellular energetics with K ATP channel-dependent membrane excitability remains elusive. Here, we identify that the response of K ATP channels to metabolic challenge is regulated by adenylate kinase phosphotransfer. Adenylate kinase associates with the K ATP channel complex, anchoring cellular phosphotransfer networks and facilitating delivery of mitochondrial signals to the membrane environment. Deletion of the adenylate kinase gene compromised nucleotide exchange at the channel site and impeded communication between mitochondria and K ATP channels, rendering cellular metabolic sensing defective. Assigning a signal processing role to adenylate kinase identifies a phosphorelay mechanism essential for efficient coupling of cellular energetics with K ATP channels and associated functions.

CD1d-restricted invariant NKT (iNKT) cells are immunoregulatory cells whose loss exacerbates diabetes in nonobese diabetic (NOD) female mice. Here, we show that the relative numbers of iNKT cells from the pancreatic islets of NOD mice decrease at the time of conversion from peri-insulitis to invasive insulitis and diabetes. Conversely, NOD male mice who have a low incidence of diabetes showed an increased frequency of iNKT cells. Moreover, administration of α-galactosylceramide, a potent activating ligand presented by CD1d, ameliorated the development of diabetes in NOD female mice and resulted in the accumulation of iNKT cells and myeloid dendritic cells (DC) in pancreatic lymph nodes (PLN), but not in inguinal lymph nodes. Strikingly, injection of NOD female mice with myeloid DC isolated from the PLN, but not those from the inguinal lymph nodes, completely prevented diabetes. Thus, the immunoregulatory role of iNKT cells is manifested by the recruitment of tolerogenic myeloid DC to the PLN and the inhibition of ongoing autoimmune inflammation.