Direct tissue MALDI-FTMS profiling of individual Cancer productus sinus glands reveals that one of three distinct combinations of crustacean hyperglycemic hormone precursor-related peptide (CPRP) isoforms are present in individual crabs

Over the past decade, mass spectrometry has become a prominent technique for identifying peptide hormones. In crustaceans, studies directed at characterizing the peptide complements present in neuroendocrine structures have generally involved the isolation of tissue from a large number of individuals, which are pooled, extracted, purified, and then analyzed via chromatographic techniques coupled with mass spectrometry. While this approach provides information on the peptides present in the population of animals used as the tissue source, data on the peptide complement present in any individual animal are lost. Direct tissue matrix assisted laser desorption/ionization Fourier transform mass spectrometry (MALDI-FTMS) of single tissues has the potential to identify differences in peptide expression between individuals. Here, we have used direct tissue MALDI-FTMS of individual sinus glands (SGs) to show that the four isoforms of crustacean hyperglycemic hormone precursor-related peptide (CPRP) identified previously from pooled Cancer productus SGs (i.e. Fu, Q., Christie, A.E., Li, L. 2005. Mass spectrometric characterization of crustacean hyperglycemic hormone precursor-related peptides (CPRPs) from the sinus gland of the crab, Cancer productus. Peptides 26, 2137-2150.) are differentially distributed in conserved patterns among individual crabs. Of the crabs examined, ∼61% of the individuals possessed Capr-CPRP I and II, but not III or IV, ∼26% Capr-CPRP I, II and III, but not IV, and ∼13% Capr-CPRP I, II and IV, but not III. Our findings set the stage for future molecular investigations on the origin(s) of this individual-specific variation in CPRP complement, as well as investigations of the function and regulation of the individual isoforms. These data also lend a cautionary note to the assumption that the peptides identified via pooled tissues reveal an accurate picture of the peptides present in any given individual.