Molecular adapter required to prevent protein hyperglycosylation of HSP90B1: during translation, associates with nascent HSP90B1 and the STT3A catalytic component of the OST-A complex and tethers them to a specialized translocon that forms a microenvironment for HSP90B1 folding (PubMed:38670073, PubMed:39509507). In the CCDC134-containing translocon, STT3A associates with the SRT pseudosubstrate motif of HSP90B1, preventing access to facultative glycosylation sites until folding is completed, preventing hyperglycosylation and subsequent degradation of HSP90B1 (PubMed:39509507). In extracellular secreted form, promotes proliferation and activation of CD8(+) T-cells, suggesting a cytokine- like function (PubMed:25125657). May inhibit ERK and JNK signaling activity (PubMed:18087676, PubMed:23070808). May suppress cell migration and invasion activity, via its effects on ERK and JNK signaling (PubMed:23070808). May also localize in the nucleus: enhances stability of the PCAF histone acetyltransferase (HAT) complex member TADA2A and thus promotes PCAF-mediated histone acetyltransferase activity (PubMed:22644376). Has a critical role in the regulation of osteogenesis and bone development (PubMed:32181939). {ECO:0000269|PubMed:18087676, ECO:0000269|PubMed:22644376, ECO:0000269|PubMed:23070808, ECO:0000269|PubMed:25125657, ECO:0000269|PubMed:32181939, ECO:0000269|PubMed:38670073, ECO:0000269|PubMed:39509507}. This is the function of ENSG00000100147 (CCDC134, coiled-coil domain containing 134).