[beta]-Bag Cell Peptide - RLRFH

Definition: 
Bag cell peptides (BCPs) are a class of small neuropeptides secreted by the bag cell neurons in the marine mollusk Aplysia(1). They trigger a series of reproductive behavior in this mollusk that finally culminates in egg-laying.

Discovery
BCPs were originally identified in the bag cell extracts of abdominal ganglion of mature Aplysia(2). They were isolated based on their ability to cause bag cell excitation.

Classification
Bag cell specific gene that encodes for the precursor form of the egg laying hormone also contains sequences that encode several small BCPs: a-BCP, b-BCP, g-BCP(2), etc.

Structural Characteristics
a-BCP is a 9 amino acid (Ala-Pro-Arg-Leu-Arg-Phe-Tyr-Ser-Leu) neuro tramsmitter whose Phe6-Tyr7 is necessary and sufficient for its function(3). It does not undergo any NH2 or COOH modifications.

Mode of action
Excitation of Bag Cell neurons triggers an afterdischarge response that results in the secretion of BCPs(4). In addition, once the afterdischarge is underway, peptide release occurs in response to both calcium influx from the extracellular space and calcium release from intracellular stores(4). Upon secretion the BCPs are packaged into discrete vesicles that are distributed throughout the central nervous system of Aplysia where they exert their functions (5).

References:
1. Rothman BS, Weir G, Dudek FE (1983a). Egg-laying hormone: direct action on the ovitestis Aplysia. Gen Comp Endocrinol, 52,134-141.
2. Rothman BS, Mayeri E, Brown RO, Yuan PM, Shively JE (1983b). Primary structure and neuronal effects of alpha-bag cell peptide, a second candidate neurotransmitter encoded by a single gene in bag cell neurons of Aplysia. Proc Natl Acad Sci, 80, 5753-5757.
3. Owens DF, Menon JG, Rotham BS (1992). Structure-activity relationship of the neurotransmitter alpha-bag cell peptide on aplysia LUQ neurons: implications regarding its inactivation in the extra cellular space. J of Neurobiology, 6, 650-70.
4. Karen JL, Ronald JK, John AC and Leonard KK (2004). Hyperosmotic media inhibit voltage-dependent calcium influx and peptide release in Aplysia neurons, J Memb. Biol., Vol 128, 41-52.
5. Hatcher NG, Sweedler JV (2008). Aplysia bag cells function as a distributed neurosecretory network. J. Neurophysiol.. 99, 333-343.