Expression patterns of C1ql4 and its cell‐adhesion GPCR Bai3 in the murine testis and functional roles in steroidogenesis

Abstract

C1q‐like 4 (C1QL4), a novel member of the C1q‐ and TNF‐related protein family, was found to be highly expressed in rodent and human testis. However, the localization, developmental, and hormonally regulated expression and biologic function of C1ql4 in the testis have not been investigated. Here, we demonstrated that C1ql4 mRNA and protein levels in murine testes gradually increased from the postnatal period to the adult stage and were up‐regulated by LH in vivo. In situ hybridization demonstrated that the distribution and expression levels of C1ql4 mRNA varied at different developmental stages, although C1ql4 mRNA was detected in the seminiferous tubule and interstitial Leydig cells. Recombinant C1QL4 did not affect cell proliferation but did increase testosterone production in TM3 Leydig cells, as well as in cultured seminiferous tubules. C1QL4‐induced testosterone secretion in Leydig cells was accompanied by increased expression of steroidogenic acute regulatory (StAR) protein and steroidogenic enzymes. During this process, the c‐Raf/extracellular signal‐regulated protein kinase kinases 1 and 2/ERK1/2/mitogen‐ and stress‐activated protein kinase‐1 and cAMP/PKA/cAMP‐responsive element binding protein signaling cascades were activated by C1QL4. The cell‐adhesion GPCR brain‐specific angiogenesis inhibitor 3 (BAI3), a putative receptor of C1QL4, was detected in the seminiferous tubule and interstitial Leydig cells during testicular development. Knockdown of Bai3 expression in Leydig cells led to a reduction in Star expression, accompanied by increases in phosphorylation of ERK1/2 and intercellular cAMP levels. However, C1QL4‐induced StAR expression was not completely suppressed in the Bai3‐deficient Leydig cells, and phosphorylation of ERK1/2 and intercellular cAMP levels were not significantly changed before and after C1QL4 stimulation. Our results suggested that although BAI3 played a role in C1QL4‐induced steroidogenesis, there was an unidentified receptor that mediated C1QL4‐activated testosterone secretion in Leydig cells through phosphorylation of ERK1/2 and up‐regulation of intracellular cAMP levels. Taken together, our results showed, for the first time to our knowledge, that C1QL4 served as a novel acute regulator of testosterone secretion, and BAI3 functioned as a new receptor that is involved in steroidogenesis in Leydig cells. BAI3‐independent ERK1/2 activation and cAMP activation mediated C1QL4‐induced testosterone secretion. This study expanded the reproductive roles and mechanisms of C1QL4 and BAI3 signaling pathways.—Tan, A., Ke, S., Chen, Y., Chen, L., Lu, X., Ding, F., Yang, L., Tang, Y., Yu, Y. Expression patterns of C1ql4 and its cell‐adhesion GPCR Bai3 in the murine testis and functional roles in steroidogenesis. FASEB J. 33, 4893–4906 (2019). http://www.fasebj.org

CTRP11 contributes modestly to systemic metabolism and energy balance

“…Although not the focus of the study, we also assessed whether loss of CTRP11 affects testosterone synthesis and skeletal muscle development based on prior findings indicating a role for CTRP11 in these two processes 38,50 . Testosterone is a potent sex steroid with demonstrable effects on systemic metabolism 72 .…”

“…[69][70][71] Although not the focus of the study, we also assessed whether loss of CTRP11 affects testosterone synthesis and skeletal muscle development based on prior findings indicating a role for CTRP11 in these two processes. 38,50 Testosterone is a potent sex steroid with demonstrable effects on systemic metabolism. 72 Skeletal muscle, being the largest and metabolically active organ by mass, plays an especially important role in modulating systemic energy balance.…”

“…A recent study also implicated a role for CTRP11/C1QL4 in steroidogenesis, based on the observations that recombinant CTRP11 can promote testosterone synthesis and secretion by TM3 Leydig cells and cultured seminiferous tubules. 50 Whether CTRP11 is required for testosterone production and secretion in the mouse testis was not determined. Additional role for CTRP11 in angiogenesis, based largely on in vitro studies, has also been noted 51 ; the physiological relevance of these findings, however, remains uncertain.…”

Beyond the Ligand: Extracellular and Transcellular G Protein–Coupled Receptor Complexes in Physiology and Pharmacology

“…In addition, C1ql3 was shown to be involved in synapse formation/maintenance underlying formation of fear memories (Martinelli et al, 2016). Peripherally, C1ql3 inhibits insulin secretion in pancreatic b cells (Gupta et al, 2018), whereas C1ql4 acts as a repressor of myoblast fusion (Hamoud et al, 2014) and was recently identified as a novel regulator of testosterone secretion in the testis (Tan et al, 2019). ADGRB3 utilizes selective domains to engage with different C1ql proteins.…”

Progress in Research on Sperm DNA Fragmentation

“…In this highly complex and orderly process, at least 150 different genes are involved [52][53][54]. Animal model studies and population studies have found that some genetic variants are closely related to spermatogenesis disorders, including neuroendocrine-related genes (GnRH, FSH, LH, FSHR, LHR), gonadal development-related genes (AZF, WT1, PRDM1, SF), meiosis-related genes (MLH1, IRF1, PRDM9, SPO11), and other genes [55][56][57][58][59][60][61][62].…”