The neuroimmune dialogue between peripheral neurons and Langerhans cells (LCs) within mucosal epithelia protects against incoming pathogens. LCs rapidly internalize human immunodeficiency virus type 1 (HIV-1) upon its sexual transmission and then trans-infect CD4⁺ T cells. We recently found that the neuropeptide calcitonin gene-related peptide (CGRP), secreted mucosally from peripheral neurons, inhibits LC-mediated HIV-1 trans-infection. In this study, we investigated the mechanism of CGRP-induced inhibition, focusing on HIV-1 degradation in LCs and its interplay with trans-infection. We first show that HIV-1 degradation occurs in endolysosomes in untreated LCs, and functionally blocking such degradation with lysosomotropic agents results in increased trans-infection. We demonstrate that CGRP acts via its cognate receptor and at a viral postentry step to induce faster HIV-1 degradation, but without affecting the kinetics of endolysosomal degradation. We reveal that unexpectedly, CGRP shifts HIV-1 degradation from endolysosomes toward the proteasome, providing the first evidence for functional HIV-1 proteasomal degradation in LCs. Such efficient proteasomal degradation significantly inhibits the first phase of trans-infection, and proteasomal, but not endolysosomal, inhibitors abrogate CGRP-induced inhibition. Together, our results establish that CGRP controls the HIV-1 degradation mode in LCs. The presence of endogenous CGRP within innervated mucosal tissues, especially during the sexual response, to which CGRP contributes, suggests that HIV-1 proteasomal degradation predominates in vivo. Hence, proteasomal, rather than endolysosomal, HIV-1 degradation in LCs should be enhanced clinically to effectively restrict HIV-1 trans-infection.

IMPORTANCE During sexual transmission, HIV-1 is internalized and degraded in LCs, the resident antigen-presenting cells in mucosal epithelia. Yet during trans-infection, infectious virions escaping degradation are transferred to CD4⁺ T cells, the principal HIV-1 targets. We previously found that the neuroimmune dialogue between LCs and peripheral neurons, innervating mucosal epithelia, significantly inhibits trans-infection via the action of the secreted neuropeptide CGRP on LCs. In this study, we investigated whether CGRP-induced inhibition of trans-infection is linked to CGRP-controlled HIV-1 degradation in LCs. We show that in untreated LCs, HIV-1 is functionally degraded in endolysosomes. In sharp contrast, we reveal that in CGRP-treated LCs, HIV-1 is diverted toward and degraded via another cytosolic protein degradative pathway, namely, the proteasome. These results establish that CGRP regulates HIV-1 degradation in LCs. As CGRP contributes to the sexual response and present within mucosal epithelia, HIV-1 proteasomal degradation in LCs might predominate in vivo and should be enhanced clinically.

粘膜上皮内的周围神经元和朗格汉斯细胞（LC）之间的神经免疫对话可防止传入的病原体。LC通过性传播迅速将1型人类免疫缺陷病毒（HIV-1）内在化，然后转染CD4 ⁺ T细胞。我们最近发现，从周围神经元粘膜分泌的神经肽降钙素基因相关肽（CGRP）抑制LC介导的HIV-1转染。在这项研究中，我们研究了CGRP诱导的抑制机制，重点研究了LCs中HIV-1的降解及其与反式相互作用的相互作用。-感染。我们首先表明，HIV-1降解发生在未经处理的LC中的溶酶体中，并且在功能上用溶溶同性剂阻断此类降解会导致转染增加。我们证明，CGRP通过其同源受体并在病毒进入后步骤中起作用，以诱导更快的HIV-1降解，但不影响溶酶体降解的动力学。我们发现，出乎意料的是，CGRP将HIV-1降解从溶酶体转移到蛋白酶体，为LC中功能性HIV-1蛋白酶体降解提供了第一个证据。这种有效的蛋白酶体降解显着抑制了反式的第一阶段-感染和蛋白酶体抑制剂，而不是溶酶体抑制剂，消除了CGRP诱导的抑制作用。在一起，我们的结果建立了CGRP控制LC中HIV-1的降解模式。内在的CGRP在神经支配的粘膜组织中的存在，尤其是在CGRP促成的性反应期间，表明HIV-1蛋白酶体降解在体内占主导地位。因此，临床上应加强蛋白酶体而不是溶酶体的HIV-1降解，以有效限制HIV-1的转染。

重要信息在性传播期间，HIV-1在黏膜上皮细胞中的常驻抗原呈递细胞LCs中被内化和降解。然而，在转染过程中，避免降解的传染性病毒粒子被转移到主要的HIV-1靶标CD4 ⁺ T细胞上。我们先前发现，LC和周围神经元之间的神经免疫对话（支配粘膜上皮细胞）通过分泌的神经肽CGRP对LC的作用显着抑制反式感染。在这项研究中，我们调查了CGRP是否会抑制反式-感染与LCs中CGRP控制的HIV-1降解有关。我们显示，在未经处理的LC中，HIV-1在溶酶体中功能性降解。与之形成鲜明对比的是，我们揭示了在CGRP处理的LC中，HIV-1向另一种胞质蛋白降解途径即蛋白酶体转移并降解。这些结果表明，CGRP可调节LC中HIV-1的降解。由于CGRP有助于性反应并存在于粘膜上皮中，LCs中的HIV-1蛋白酶体降解可能在体内占主导地位，应在临床上予以加强。