CD109 is a multifunctional coreceptor, whose function has been widely studied in tumor progression and metastasis. One of the reported primary roles of CD109 involves down-regulating TGFβ signaling. However, the role of CD109 in central nervous system, especially neurodegenerative disease, is barely known. Here, we examined the expression changes and cellular location of CD109 and TGFβ/SMAD pathway molecules in lumbar spinal cord of SOD1-G93A mice, and explored the role and mechanism of CD109 on LPS-treated BV2 microglia and primary microglia derived from SOD1-G93A mice. Our results showed an increased expression of CD109 and TGFβ/SMAD pathway molecules in lumbar spinal cord of SOD1-G93A mice. Further cellular localization analysis demonstrated that proliferating microglia contributed mainly to the upregulation of CD109 and TGFβ1. Moreover, CD109 intervention in vitro partially reduced inflammatory response and TGFβ/SMAD pathway activation in both LPS-treated BV2 microglia and primary SOD1-G93A microglia. Thus, CD109 was involved in pathogenesis of ALS mice, and interventions targeting on CD109 modulation could be a potential therapeutic strategy for ALS.Copyright © 2024. Published by Elsevier Inc.