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Abstract: We have discovered a family of small secreted proteins in Homo sapiens and Mus musculus. The IGF-like (IGFL) genes encode proteins of approximately 100 amino acids that contain 11 conserved cysteine residues at fixed positions, including two CC motifs. In H. sapiens, the family is composed of four genes and two pseudogenes that are referred as IGFL1 to IGFL4 and IGFL1P1 and IGFL1P2, respectively. Human IGFL genes are clustered together on chromosome 19 within a 35-kb interval. M. musculus has a single IGFL family member that is located on chromosome 7. Further, evolutionary analysis shows a lack of direct orthology between any of the four human members and the mouse gene. This relationship between the mouse and the human family members suggests that the multiple members in the human complement have arisen from recent duplication events that appear limited to the primate lineage. Structural considerations and sequence comparisons would suggest that IGFL proteins are distantly related to the IGF superfamily of growth factors. IGFL mRNAs display specific expression patterns; they are expressed in fetal tissues, breast, and prostate, and in many cancers as well, and this pattern is consistent with that of the IGF family members. [Copyright &y& Elsevier]

An emerging series of papers has identified new receptor proteins that predict seven-transmembrane pass topologies. We have consolidated this family to 11 human genes and have named the family PAQR, after two of the initially described ligands (progestin and adipoQ receptors). This protein family has ancient evolutionary roots, with identified homologs found in eubacteria. To date, published data indicate that the prokaryotic members of this family appear to encode hemolysin-type proteins, while in eukaryotes, PAQR proteins encode functional receptors with a broad range of apparent ligand specificities. We provide the complete human and mouse complement of this family, suggest a conserved structure/topology with invariant intracellular amino acid residues, and have measured mRNA expression levels for these genes across a range of human tissues. [ABSTRACT FROM AUTHOR]