The effect of proctolin analogues and other peptides on locust oviduct muscle contractions

Proctolin, an insect neuropeptide

“…The agonistic properties of analogues iodinated at the aromatic ring of Tyr-2 suggest a possible use of these [ 125 I]-derivative to identify and characterize the proctolin receptor [67]. These remarks are supported by studies of Puiroux et al [79] on the proctolin receptor in the oviduct of L. migratoria, where iodinated proctolin derivatives have high myostimulatory activity. [h-MeTyr 2 ]-Proctolin [67] (a peptide with no agonistic properties) has high antagonistic activity on the foregut of S. gregaria.…”

“…Arg-Tyr-Leu-X 4 -Thr; X 4 = D-Pro [27] Pro(4-OMe); Thz; ihomo-Pro; Ach; Sar [74,82] Arg-Tyr-Leu-Pro-X 5 ; X 5 = D-Thr; Ser; Thr-NH 2 [27,79,83] MeThr [67] D-Val [83] Other proctolin analogues Arg-Tyr-Leu-Pro-Thr-NH 2 , [27] Tyr-Leu-Pro-Thr, Leu-Pro-Thr [79] Arg-Tyr-Leu-Pro-Thr-Ala Tyr-Arg-Tyr, Leu-Pro-Thr, Tyr-Leu [67] H-Cys-Arg-Tyr-Leu-Pro-Thr-Ç ¹¹¹¹¹¹¹¹¹¹¹¹¹¹¹º ys-OH, [79] Arg-Tyr-Leu-Pro Phe(p-NH 2 )-Leu-Pro-Thr, [69,74] Phe(p-NO 2 )-Leu-Pro-Thr, Phe(3-CO 2 Et,4-OMe)-Leu-Pro-Thr Arg-D-Tyr-Leu-D-Pro-Thr, [83,91] Arg-Tyr-D-Leu-D-Pro-Thr [27] sag [51] sag [51] np ag [78] np np Phe(OEt) -ag [69] in [69] np sag [69] Phe(p-NH 2 ) -sag [51] sag [51] ag [77] ag [78] sag [69] ag [77] Phe(p-NO 2 ) -sag [51] sag [51] ag [78] ag [31] -Phe(p-NMe 2 ) -sag [51] ag [51] ag [78] --Dopa -sag [85] ag [76] ag [85] ag [78] wag [55] ag [76] Tyr(m-NH 2 ) -ag [31] ag [31] - [Orn(iPr) 1 ]...…”

“…The role of the aromatic acid residue at position 2 has been more fully discussed in the literature [21,27,50,67,79]. Thus, replacement of the Tyr 2 by Phe or D-Tyr resulted in loss of stimulatory activity on the proctodeal muscle on P. americana [21,27].…”

“…These results suggest that the presence of Pro-4 is essential for the cardiotropic properties of proctolin in insects. Among the proctolin analogues modified in position 5 of the peptide skeleton (Table 3) only C-terminally modified analogues with Ala [27], MeThr [67], Val, Ile, D-Ile, Asn, Gln or Ser [83] replacements showed agonistic or weak-agonistic effects on the oviduct of L. migratoria [79] or on the foregut of S. gregaria [67,83] or in the heart of T. molitor [83]. These data suggest that the C-terminal Thr residue plays an important role for myotropic activity in insects.…”

The SepOvotropin: A New Ovarian Peptide Regulating Oocyte Transport in Sepia officinalis

“…A similar peptide was identified in the marine gastropod Aplysia californica. This peptide called attractin was released from egg cordons provoking the gathering of mature adults for reproduction [15]. The SepOvotropin could be one of these chemical messengers involved in the gathering of mature adults and in egg-laying.…”