Pedro Roda-Navarro

The human C-type lectin CLECSF8 is a novel monocyte/macrophage endocytic receptor

Cell surface lectin receptors play important roles in the function of macrophages. Herein, we have identified and characterized the human orthologue of the mouse Mcl/Clecsf8.Human CLECSF8 codes for a typeu2004II membrane glycoprotein of 215 amino acids that belongs to the human calcium‐dependent lectin family (C‐type lectin). The cytoplasmic tail of CLECSF8 lacks consensus signaling motifs and its extracellular region shows a single carbohydrate recognition domain (CRD). The CLECSF8 gene has been localized on the telomeric region of the NK gene complex on chromosome 12p13 close to MINCLE. CLECSF8 mRNA shows a monocyte/macrophage expression pattern. Biochemical analysis of CLECSF8 on transiently transfected cells showed a glycoprotein of 30u2004kDa. Cross‐linking of the receptor leads to a rapid internalization suggesting that CLECSF8 constitutes and endocytic receptor.

Dynamic Redistribution of the Activating 2B4/SAP Complex at the Cytotoxic NK Cell Immune Synapse

The 2B4 molecule (CD244) has been described as a coreceptor in human NK cell activation. However, the behavior of 2B4 during the cytotoxic NK cell immune synapse (NK-IS) formation remains undetermined. In this study, we demonstrate the redistribution of 2B4 and the signaling adaptor molecule, signaling lymphocyte activation molecule-associated protein (SAP), to the cytotoxic NK-IS upon formation of conjugates between resting NK cells and EBV-infected 721.221 human cells. Confocal microscopy showed that 2B4 localized at the central supramolecular activation cluster, surrounded by a peripheral supramolecular activation cluster containing talin within NK cell and ICAM-1 on target cells. Videomicroscopy studies with 2B4-GFP-transfected NK cells revealed that 2B4 redistributed to cytotoxic NK-IS as soon as the cell contact occurred. Simultaneously, a SAP-GFP also clustered at the contact site, where it remained during the interaction period. The 2B4 molecular clusters remained bound to the target cell even after NK cell detachment. These results underscore the function of 2B4 as an adhesion molecule and suggest a relevant role in the initial binding, scanning of target cells, and formation of cytotoxic NK-IS. Finally, these findings are indicative of an important role of the activating 2B4/signaling lymphocyte activation molecule-associated protein complex during the recognition of EBV-infected cells.

Cloning of human DECTIN-1, a novel C-type lectin-like receptor gene expressed on dendritic cells

Abstract. We identified a new Ca2+-dependent lectin-like receptor gene, DECTIN-1 (HGMW-approved symbol CLECSF12), the human orthologue of mouse Dectin-1, coding for a putative typexa0II transmembrane glycoprotein with an extracellular C-type lectin-like domain. The gene structure and two alternative spliced forms of DECTIN-1 are described. The DECTIN-1 gene was localized in the natural killer gene complex on human Chromosome 12p12.3–p13.2, between OLR1 and CD94 (position 21.8xa0cM on the genetic map). The DECTIN-1 gene is highly expressed at the mRNA level in dendritic cells and is not further up-regulated during the maturation of these cells with tumor necrosis factor-α. The DECTIN-1 gene therefore represents a novel human member of the C-type lectin-like receptor gene family preferentially expressed in dendritic cells.

Human KLRF1, a novel member of the killer cell lectin-like receptor gene family: molecular characterization, genomic structure, physical mapping to the NK gene complex and expression analysis.

The human NK gene complex localized on chromosome 12p12.3u2009–u2009p13.2 codes for several lectin‐like receptor genes expressed by NK cells as well as by other hematopoietic cells. In this study, by using the expressed sequence tag database we identified a novel receptor gene, designated as killer cell lectin‐like receptor, subfamily F, member 1 (KLRF1), encoding a putative type II transmembrane glycoprotein. The KLRF1 gene has been localized on the high‐resolution physical map of chromosome 12p. The genomic structure of the KLRF1 gene and the existence of one spliced variant are also described. KLRF1 was expressed at the mRNA level in peripheral blood leukocytes, activated NK cells, monocytes and NK and myeloid cell lines. The presence of two immunoreceptor tyrosine‐based inhibitory‐like motifs within the cytoplasmic tail of KLRF1 suggests an inhibitory role in NK cell and monocyte activity.

Molecular and genomic characterization of human DLEC, a novel member of the C-type lectin receptor gene family preferentially expressed on monocyte-derived dendritic cells.

We have identified a novel gene encoding a protein designated DLEC (dendritic cell lectin), which is a type II membrane glycoprotein of 213 amino acids and belongs to the human calcium‐dependent (C‐type) lectin family. The cytoplasmic tail of DLEC lacks consensus signaling motifs and its extracellular region shows a single carbohydrate recognition domain (CRD), closest in homology to thedendritic cell immunoreceptor (DCIR) CRD. The DLEC gene has been localized linked to DCIR on the telomeric region of the NK gene complex. RT‐PCR and Northern blot analyses show that DLEC mRNA is preferentially expressed in monocyte‐derived dendritic cells.

Molecular characterization of two novel alternative spliced variants of the KLRF1 gene and subcellular distribution of KLRF1 isoforms.

The killer cell lectin-like receptor (KLR) family is formed by type II transmembrane glycoproteins with a single extracellular C-type lectin-like domain (CTLD). Some of these glycoproteins are involved in the regulation of natural killer cell activity. Recently, we have described the molecular characterization of the KLRF1 gene and the existence of one alternative spliced form, lacking the stalk region of the extracellular domain. In this work we describe two novel KLRF1 alternative spliced variants coding for truncated proteins lacking the CTLD. In addition, we present the biochemical analysis of the KLRF1 protein and the subcellular distribution of all KLRF1 isoforms expressed in heterologous transfectants.