Peptidomics of a single identified neuron reveals diversity of multiple neuropeptides with convergent actions on cellular excitability.

In contrast to classical transmitters, the detailed structures and cellular and synaptic actions of neuropeptides are less well described. Peptide mass profiling of single identified neurons of the mollusc Lymnaea stagnalis indicated the presence of 17 abundant neuropeptides in the cardiorespiratory neuron, visceral dorsal 1 (VD1), and a subset of 14 peptides in its electrically coupled counterpart, right parietal dorsal 2. Altogether, based on this and previous work, we showed that the high number of peptides arises from the expression and processing of four distinct peptide precursor proteins, including a novel one.

Stimulus-dependent regulation and cellular expression of genes encoding neuropeptides, prohormone convertases, alpha-amidating enzyme and 7B2 in identified Lymnaea neurons.

Synthesis of bioactive peptides is regulated by several post-translational processing events, including cleavage of peptides from a prohormone, and chemical modifications. Using quantitative in situ hybridization and neuron-specific macro-arrays, we first demonstrated cell-type specific expression levels of transcripts encoding prohormone convertases, peptide alpha-amidating enzyme as well as the chaperone 7B2 in Lymnaea neurons. Second, we demonstrated a strict correlation between alpha-amidating enzyme and its neuropeptide substrates.

The sorLA cytoplasmic domain interacts with GGA1 and -2 and defines minimum requirements for GGA binding.

We report that the Vps10p domain receptor sorLA binds the adaptor proteins GGA1 and -2, which take part in Golgi-endosome sorting. The GGAs bind with differential requirements via three critical residues in the C-terminal segment of the sorLA cytoplasmic tail. Unlike in sortilin and the mannose 6-phosphate receptors, the GGA-binding segment in sorLA contains neither an acidic cluster nor a dileucine.