Locke M, Kiss A, Sass M
Central Food Research Institute of Hungary, Budapest, Hungary.
Tissue Cell. 1994 Oct;26(5):707-34. doi: 10.1016/0040-8166(94)90055-8.
The distribution of integument peptides in relation to chitin and structural features has been studied in the surface epidermis of the caterpillar of Calpodes ethlius by immunoblotting and immunogold labelling using antibodies prepared to peptides isolated from lamellate endocuticle or from hemolymph. The intermoult cuticle consists of an epicuticle, an endocuticle of many chitin containing lamellae, and a chitin containing assembly zone directly above the apical epidermal microvilli and the perimicrovillar space. During the intermoult, the epidermis secretes peptides constitutively, that is, secretory vesicles containing peptides exocytose without accumulating, traverse the perimicrovillar space and form lamellae in the assembly zone. At moulting, the epidermis deposits ecdysial droplets in addition. These interrupt the last few lamellae which later go on to become the perforated ecdysial membrane. The integument is involved with four routing classes of peptide. Secretion is apical into the cuticle (C), basal into the hemolymph (H), bidirectional (BD), or transported to the cuticle across the epidermis from the hemolymph (T). Some peptides change their routing at moulting. There are several patterns of localization. (1) C and BD cuticular peptides occur mainly in chitin containing lamellate cuticle. (2) Some are also present in epicuticle, and are therefore not obligatorily linked to chitin or matrix between chitin fibers. Cuticular peptides that also occur in the hemolymph are glycosylated, whereas most that are only secreted apically into the cuticle are not. All BD but few C peptides carry alpha-D-glucose/alpha-D-mannose. Some C and BD peptides carry N-acetyl glucosamine. (3) C36 extracted from cuticle has most N-acetyl glucosamine and colocalizes with chitin rather than the protein matrix. It is therefore probably the main link between chitin fibers and the matrix. (4) H235 is barely detectable at the apical cell surface during the intermoult but is abundant at moulting around and below the ecdysial droplets. (5) T66 occurs in intermoult lamellate cuticle. At moulting, alone among the peptides examined, it is in ecdysial droplets. Intermoult C and BD peptides are not in ecdysial droplets but continue to be present in the ecdysial membrane, suggesting that constitutive secretion is independent from the exocytosis of transported moult peptides. T66 differs from most hemolymph peptides in that it does not carry N-acetyl glucosamine or alpha-D-glucose/alpha-D-mannose. (6) Weakly reacting BD peptides (and some H peptides barely detectable in cuticle) localize near the apical surface. Their distribution therefore favours apical secretion and retrieval as a mechanism for basal secretion.
利用针对从层状内表皮或血淋巴中分离出的肽段制备的抗体，通过免疫印迹和免疫金标记技术，研究了埃氏角纹夜蛾幼虫体表表皮中与几丁质及结构特征相关的体表肽的分布情况。蜕皮间期的表皮由上表皮、许多含几丁质薄片的内表皮以及直接位于顶端表皮微绒毛和微绒毛周围间隙上方的含几丁质组装区组成。在蜕皮间期，表皮持续分泌肽段，即含有肽段的分泌小泡通过胞吐作用排出而不积累，穿过微绒毛周围间隙并在组装区形成薄片。在蜕皮时，表皮还会沉积蜕皮液滴。这些液滴会中断最后几层薄片，这些薄片随后会变成有孔的蜕皮膜。体表涉及四类肽的运输途径。分泌途径为顶端分泌到表皮（C）、基部分泌到血淋巴（H）、双向分泌（BD）或从血淋巴穿过表皮运输到表皮（T）。一些肽在蜕皮时会改变其运输途径。存在几种定位模式。（1）C类和BD类表皮肽主要存在于含几丁质的层状表皮中。（2）有些也存在于上表皮中，因此并非必然与几丁质或几丁质纤维之间的基质相连。同时存在于血淋巴中的表皮肽是糖基化的，而大多数仅顶端分泌到表皮中的肽则不是。所有BD类肽但只有少数C类肽携带α-D-葡萄糖/α-D-甘露糖。一些C类和BD类肽携带N-乙酰葡糖胺。（3）从表皮中提取的C36含有最多的N-乙酰葡糖胺，并且与几丁质而非蛋白质基质共定位。因此，它可能是几丁质纤维与基质之间的主要连接物。（4）H235在蜕皮间期顶端细胞表面几乎检测不到，但在蜕皮时在蜕皮液滴周围及下方大量存在。（5）T66存在于蜕皮间期的层状表皮中。在蜕皮时，在所检测的肽中，只有它存在于蜕皮液滴中。蜕皮间期的C类和BD类肽不在蜕皮液滴中，但仍存在于蜕皮膜中，这表明持续分泌独立于运输的蜕皮肽的胞吐作用。T66与大多数血淋巴肽不同，它不携带N-乙酰葡糖胺或α-D-葡萄糖/α-D-甘露糖。（6）反应较弱的BD类肽（以及一些在表皮中几乎检测不到的H类肽）定位在顶端表面附近。因此它们的分布有利于顶端分泌和回收，作为基部分泌的一种机制。
