The neuroendocrine protein 7B2 plays a crucial role in the maturation and activity regulation of prohormone convertase 2 (PC2). To elucidate the relationship between 7B2 and PC2 expression in endocrine tissues, we generated synthetic peptide antibodies in guinea pigs. The antigenic peptide sequences were selected to correspond to three different positions in the rat amino acid (aa) sequence: The N-terminal aa 1–14 is situated immediately following the signal sequence, the middle aa 77–90 contains a part of the proPC2 activation domain, and the C-terminal aa 156–168 functions to suppress PC2 activity. These antibodies demonstrated specific reactivity across a diverse array of animal species. The reactivity of these antibodies differed, suggesting that the molecular form of 7B2 differs depending on the endocrine cell, and a different expression pattern was demonstrated in rat and dog pituitary intermediate cells. The colocalization of 7B2 and PC2 in prolactin (PRL) granules in rat pituitary mammotrophs supports the interaction between these proteins. However, the expression intensities of these proteins did not correspond, and epitope-related disparities were detected. These results may be indicative of alterations in the molecular state associated with the dynamics of the interaction between 7B2 and PC2:
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