Expression of the SCAMP-4 gene, a new member of the secretory carrier membrane protein family, is repressed by progesterone in brain regions associated with female sexual behavior

Rodent female reproductive behavior is facilitated by the genomic targets o f estrogen (E) and progesterone (P) in neuroendocrine regions of the brain. Using the differential display-PCR technique to identify these targets we discovered a novel hormone-sensitive mRNA in the female rat brain that is s ubstantially reduced in the ventromedial hypothalamus (VMH) after 3 h of P treatment, following 24 h of E priming. Northern blots show that it is a si ngle transcript of approximately 1.7 kb. The sequence of the corresponding full-length cDNA indicates that this gene is the rat homolog of mouse SCAMP -4, the fourth member identified in a family of proteins known as secretory carrier membrane proteins (SCAMPs). In situ hybridization studies show tha t SCAMP-4 mRNA is relatively low throughout the rat forebrain, with the hig hest levels observed in the VMH, habenula and hippocampus. The SCAMP-Lt mes sage is also less abundant in the habenula and VMH during proestrus, when c irculating levels of E and P are at their peak, than during diestrus-l when circulating hormone levels are low. Amino acid sequence analysis indicates that SCAMP-4 lacks the putative calcium binding and leucine zipper structu res, as well as protein-protein interacting NPF domains common among most S CAMP family members, but is the only member identified to date to contain a putative protein kinase C (PRC) phosphorylation site. Fluorescent microsco py of cells transfected with a SCAMP-4/GFP fusion construct reveals distinc t fluorescence in subcellular aggregates that may contain secretory vesicle s. in addition to our results in the VMH, the finding of high levels of SCA MP-4 message in the habenula, a brain area rich in mast cells, together wit h previous reports linking mast cell secretion with courtship behavior also suggest a possible role for SCAMP-4 in reproductive behaviors associated w ith mast cell activity in the central nervous system (CNS). (C) 2001 Elsevi er Science B.V. All rights reserved.