Previous studies showed that chromogranin A (CgA), a glycoprotein stored and co-released with various hormones by neuroendocrine cells and neurons, can modulate cell adhesion. We have investigated the structureactivity relationships of CgA using fibroblasts and coronary artery smooth muscle cells in adhesion assays. A recombinant CgA fragment 1-78 and a peptide 7-57 containing reduced and alkylated cysteines (Cys 17 and Cys 38 ) induced cell adhesion after adsorption onto solid phases at 50 -100 nM. Peptides lacking the disulfide loop region, including residues 47-68, 39 -59, and 39 -68, induced cell adhesion, either bound to solid phases at 200 -400 nM or added to the liquid phase at 5-10 M, whereas peptide 60 -68 was inactive, suggesting that residues 47-57 are important for activity. The effect of CgA-(1-78) was blocked by anti-CgA antibodies against epitopes including residues Arg 53 , His 54 , and Leu 57 . Substitutions of residues His 54 , Gln 55 , and Asn 56 with alanine decreased the cell adhesion activity of peptide 47-68. These results suggest that the region 47-57 (RILSILRHQNL) contains a cell adhesion site and that the disulfide bridge is not necessary for the proadhesive activity. The ability of soluble peptides to elicit proadhesive effects suggests an indirect mechanism. The high sequence conservation and accessibility to antibodies suggest that this region is important for the physiological role of CgA.

ABSTRACTDevelopment of the cortical circuits for sensory-motor processing require the coordinated integration of both columnar and long-range synaptic connections. To understand how this occurs at the level of individual neurons we have explored the timeline over which vasoactive intestinal peptide (VIP)-expressing interneurons integrate into mouse somatosensory cortex. We find a distinction in emergent long-range anterior-motor and columnar glutamatergic inputs onto layer (L)2 and L3 VIP+ interneurons respectively. In parallel, VIP+ interneurons form efferent connections onto both pyramidal cells and interneurons in the immediate column in an inside-out manner. Cell-autonomous deletion of the fate-determinant transcription factor, Prox1, spares long-range anterior-motor inputs onto VIP+ interneurons, but leads to deficits in local connectivity. This imbalance in the somatosensory circuit results in altered spontaneous and sensory-evoked cortical activity in vivo. This identifies a critical role for VIP+ interneurons, and more broadly interneuron heterogeneity, in formative circuits of neocortex.