Search

Representation of the chimera CIRB.

Primers used for Expression profiles of cytotoxicity effectors in NK92, NK92IL2 and NK92CIRB.

Supplementary Figure Legend including Supplementary Table 1: Primers used for Expression profiles of cytotoxicity effectors in NK92, NK92IL2 and NK92CIRB. Supplementary Tabel 2: Impact of direct contact with cancer cells on NK cells expression profiles of natural cytotoxicity and effectors. Supplementary Figure 1: Representation of the chimera CIRB. Supplementary Figure 2: Cell growth of NK92IL2 and NK92CIRB cell lines.

IL2 is an immunostimulatory cytokine for key immune cells including T cells and natural killer (NK) cells. Systemic IL2 supplementation could enhance NK-mediated immunity in a variety of diseases ranging from neoplasms to viral infection. However, its systemic use is restricted by its serious side effects and limited efficacy due to activation of T regulatory cells (Tregs). IL2 signaling is mediated through interactions with a multi-subunit receptor complex containing IL2Rα, IL2Rβ, and IL2Rγ. Adult natural killer (NK) cells express only IL2Rβ and IL2Rγ subunits and are therefore relatively insensitive to IL2. To overcome these limitations, we created a novel chimeric IL2-IL2Rβ fusion protein of IL2 and its receptor IL2Rβ joined via a peptide linker (CIRB). NK92 cells expressing CIRB (NK92CIRB) were highly activated and expanded indefinitely without exogenous IL2. When compared with an IL2-secreting NK92 cell line, NK92CIRB were more activated, cytotoxic, and resistant to growth inhibition. Direct contact with cancer cells enhanced the cytotoxic character of NK92CIRB cells, which displayed superior in vivo antitumor effects in mice. Overall, our results showed how tethering IL2 to its receptor IL2Rβ eliminates the need for IL2Rα and IL2Rβ, offering a new tool to selectively activate and empower immune therapy. Cancer Res; 77(21); 5938–51. ©2017 AACR.

Type-A γ-aminobutyric acid receptors (GABA(A)Rs) are pentameric ligand-gated chloride channels that mediate fast inhibitory signalling in neural circuits( 1,2 ) and are modulated by essential medicines including general anaesthetics and benzodiazepines( 3 ). Human GABA(A)R subunits are encoded by 19 paralogous genes which can, in theory, give rise to 495,235 receptor types. Yet, the principles governing the formation of pentamers, the permutational landscape of receptors that may emerge from a subunit set and the impact this has on GABA-ergic signalling remain largely unknown. Here, we use cryogenic electron microscopy (cryo-EM) to determine structures of extrasynaptic GABA(A)R assembled from α4, β3 and δ subunits, and their counterparts incorporating γ2 instead of δ subunits. In each case we could identify two receptor subtypes with distinct stoichiometries and arrangements, all four differing from those previously observed for synaptic, α1-containing receptors( 4–7 ). This, in turn, affects receptor responses to physiological and synthetic modulators by creating or eliminating ligand binding sites at subunit interfaces. We provide structural and functional evidence that selected GABA(A)R arrangements can act as coincidence detectors, simultaneously responding to two neurotransmitters, GABA and histamine. Using assembly simulations and single-cell RNA sequencing data( 8,9 ), we calculate upper bounds for receptor diversity in recombinant systems and in vivo. We propose that differential assembly is a pervasive mechanism for regulating the physiology and pharmacology of GABA(A)Rs.

Extrasynaptic γ-aminobutyric acid type A receptors (GABAARs),which contribute generalized inhibitory tone to the mammalian brain, are major targets for general anesthetics. To identify anesthetic binding sites in an extrasynaptic GABAAR, we photolabeled human α4β3δ GABAARs purified in detergent with [3H]azietomidate and a barbiturate, [3H]R-mTFD-MPAB, photoreactive anesthetics that bind with high selectivity to distinct but homologous intersubunit binding sites in the transmembrane domain of synaptic α1β3γ2 GABAARs. Based upon 3H incorporation into receptor subunits resolved by SDS-PAGE, there was etomidate-inhibitable labeling by [3H]azietomidate in the α4 and β3 subunits and barbiturate-inhibitable labeling by [3H]R-mTFD-MPAB in the β3 subunit. These sites did not bind the anesthetic steroid alphaxalone, which enhanced photolabeling, or DS-2, a δ subunit-selective positive allosteric modulator, which neither enhanced nor inhibited photolabeling. The amino acids labeled by [3H]azietomidate or [3H]R-mTFD-MPAB were identified by N-terminal sequencing of fragments isolated by HPLC fractionation of enzymatically digested subunits. No evidence was found for a δ subunit contribution to an anesthetic binding site. [3H]azietomidate photolabeling of β3Met-286 in βM3 and α4Met-269 in αM1 that was inhibited by etomidate but not by R-mTFD-MPAB established that etomidate binds to a site at the β3+-α4- interface equivalent to its site in α1β3γ2 GABAARs. [3H]Azietomidate and [3H]R-mTFD-MPAB photolabeling of β3Met-227 in βM1 established that these anesthetics also bind to a homologous site, most likely at the β3+-β3- interface, which suggests a subunit arrangement of β3α4β3δβ3.