The abilities of 18 synthetic peptides to target a carrier protein to the nucleus following microinjection into the cytoplasm of HeLa cells were determined. Eight of the sequences chosen for synthesis were based on published nuclear targeting regions as determined by gene fusion and deletion experiments. Six of these sequences were found to be effective when mimicked by a synthetic peptide and conjugated to a carrier protein.One additional peptide was based on a region of lamin L,, a nuclear protein from Xenopus laevis, in which the nuclear targeting region had not been previously investigated. This peptide was also able to target a carrier protein to the nucleus. Eight other peptides which resemble the known targeting signals had little or no nuclear targeting ability. Peptides which were able to target a carrier protein to the nucleus did so within 45 min of injection into the cytoplasm. Two peptides with little or no apparent nuclear targeting ability after 45 min were examined for longer times as well. No increase in nuclear accumulation was observed between 45 min and 4 h after cytoplasmic injection. Comparison of the sequences which were effective at nuclear targeting with those that were not revealed a possible consensus sequence for peptide-mediated nuclear transport.Proteins destined for the nucleus in eucaryotic cells enter through large pore structures distributed evenly over the nuclear envelope. Entry An alternative to genetic manipulation has been chemical synthesis of a peptide which mimics a putative nuclear targeting region. The nuclear targeting sequence of the simian virus 40 (SV40) T antigen has been synthesized and cross-linked to a variety of nonnuclear carrier proteins, such as serum albumin, immunoglobulin G, and ferritin. These conjugates are translocated to the nucleus following microinjection into the cytoplasm of cells (6,14). Changing one amino acid in the sequence (lysine 128 to either threonine or asparagine) yields a dramatic reduction in the degree of transport of the peptide conjugate into nuclei (6, 14). The results of these peptide "'mutations" are consistent with results obtained by mutational analysis of the T antigen itself (10, 13).We synthesized 2 SV40 T-antigen nuclear targeting peptides and 16 others to determine the general utility of peptide-mediated translocation and to define further the sequence requirements for nuclear transport. We found that some but not all of the genetically defined transport sequences could be mimicked by peptide conjugates. Although all of the peptides capable of directing nuclear transport contain a cluster of basic residues, this in itself is not * Corresponding author. sufficient for transport. Most of the nontargeting peptides also contain either three or four basic residues clustered in a short sequence. A comparison of the amino acid sequences of nuclear targeting versus nontargeting peptides has led us to propose a consensus sequence for such peptides. MATERIALS AND METHODSPeptide synthesis. All of the peptides listed in Table 1 wer...

Reduced N-methyl-D-aspartate-receptor (NMDAR) signaling has been associated with schizophrenia, autism and intellectual disability. NMDAR-hypofunction is thought to contribute to social, cognitive and gamma (30–80 Hz) oscillatory abnormalities, phenotypes common to these disorders. However, circuit-level mechanisms underlying such deficits remain unclear. This study investigated the relationship between gamma synchrony, excitatory–inhibitory (E/I) signaling, and behavioral phenotypes in NMDA-NR1neo−/− mice, which have constitutively reduced expression of the obligate NR1 subunit to model disrupted developmental NMDAR function. Constitutive NMDAR-hypofunction caused a loss of E/I balance, with an increase in intrinsic pyramidal cell excitability and a selective disruption of parvalbumin-expressing interneurons. Disrupted E/I coupling was associated with deficits in auditory-evoked gamma signal-to-noise ratio (SNR). Gamma-band abnormalities predicted deficits in spatial working memory and social preference, linking cellular changes in E/I signaling to target behaviors. The GABAB-receptor agonist baclofen improved E/I balance, gamma-SNR and broadly reversed behavioral deficits. These data demonstrate a clinically relevant, highly translatable neural-activity-based biomarker for preclinical screening and therapeutic development across a broad range of disorders that share common endophenotypes and disrupted NMDA-receptor signaling.

The binding of interferons to distinct cell surface receptors leads to the induction of synthesis of several unique polypeptides and their corresponding mRNAs (1)(2)(3)(4)(5)(6) (8,9). One of these cDNA clones is complementary to the mRNA for a 56-kDa protein (8), and the other, to the mRNA for 2',5'-oligo(A) synthetase (9), both of which are prominent IFN-induced protein products (7). Whether this increase in specific mRNA is based on increased transcription and/or increased stabilization of the mRNA in the cytoplasm has not been determined.In fact, whether transcriptional increases underlie the numerous biologic effects mediated by the binding of peptide hormones, growth factors, and lectins to their specific plasma membrane receptors is at present largely unknown. It is also unclear whether a polypeptide can effect an increase in specific mRNA concentration, particularly by transcriptional control, without entering the cell. Molecules such as cyclic AMP or Ca2+ or analogous "second messengers" could mediate the transcriptional stimulation of specific genes after an initial hormone-receptor interaction. Likewise, the effect of intracellular tyrosine kinase activities of membrane receptor proteins is under intense investigation, but no specific transcriptional activations have been documented as a result of these enzyme activities.A few cases have been analyzed that support the hypothesis of second messengers as transcriptional activators. Thyrotropin-releasing hormone (TRH) and epidermal growth factor (EGF) increase transcription of the prolactin gene in a pituitary cell line (10, 11). The effects of TRH can be mimicked by cyclic AMP treatment of the pituitary tumor cells. EFG-induced prolactin mRNA accumulation requires extracellular Ca2 , which implies that increased free intracellular

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RNA encoding the rat serotonin 5-HT