Leucine zipper transcription factor-like 1 binds adaptor protein complex-1 and 2 and participates in trafficking of transferrin receptor 1

Abstract

LZTFL1 participates in immune synapse formation, ciliogenesis, and the localization of ciliary proteins, and knockout of LZTFL1 induces abnormal distribution of heterotetrameric adaptor protein complex-1 (AP-1) in the Lztfl1-knockout mouse photoreceptor cells, suggesting that LZTFL1 is involved in intracellular transport. Here, we demonstrate that in vitro LZTFL1 directly binds to AP-1 and AP-2 and coimmunoprecipitates AP-1 and AP-2 from cell lysates. DxxFxxLxxxR motif of LZTFL1 is essential for these bindings, suggesting LZTFL1 has roles in AP-1 and AP-2-mediated protein trafficking. Since AP-1 and AP-2 are known to be involved in transferrin receptor 1 (TfR1) trafficking, the effect of LZTFL1 on TfR1 recycling was analyzed. TfR1, AP-1 and LZTFL1 from cell lysates could be coimmunoprecipitated. However, pull-down results indicate there is no direct interaction between TfR1 and LZTFL1, suggesting that LZTFL1 interaction with TfR1 is indirect through AP-1. We report the colocalization of LZTFL1 and AP-1, AP-1 and TfR1 as well as LZTFL1 and TfR1 in the perinuclear region (PNR) and the cytoplasm, suggesting a potential complex between LZTFL1, AP-1 and TfR1. The results from the disruption of adaptin recruitment with brefeldin A treatment suggested ADP-ribosylation factor-dependent localization of LZFL1 and AP-1 in the PNR. Knockdown of AP-1 reduces the level of LZTFL1 in the PNR, suggesting that AP-1 plays a role in LZTFL1 trafficking. Knockout of LZTFL1 reduces the cell surface level and the rate of internalization of TfR1, leading to a decrease of transferrin uptake, efflux, and internalization. However, knockout of LZTFL1 did not affect the cell surface levels of epidermal growth factor receptor and cation-independent mannose 6-phosphate receptor, indicating that LZTFL1 specifically regulates the cell surface level of TfR1. These data support a novel role of LZTFL1 in regulating the cell surface TfR1 level by interacting with AP-1 and AP-2.

Identification of LZTFL1 as a candidate effector gene at a COVID-19 risk locus

“…The association of 3p21.31 variants with susceptibility to SARS-CoV-2 infection, as well as disease severity, highlights the importance of the respiratory epithelium for this locus 11 . LZTFL1 encodes a cytosolic leucine zipper protein, which associates with the epithelial marker E-cadherin and is involved in the trafficking of numerous signaling molecules 45,[71][72][73][74] . We note that upregulation of LZTFL1 in the context of malignancy inhibits EMT 45,59,60 , a pathway known to be part of both wound healing and immune responses [53][54][55][56] .…”

Semantic and population analysis of the genetic targets related to COVID-19 and its association with genes and diseases

“…The LZTFL1 gene codes for a leucine zipper protein, which associates with E-cadherin and participates in the circulation of a variety of signaling molecules (84, 85). The gene is expressed in pulmonary epithelial cells, among others, and has been recently identified as a target for a probable causative variant related to COVID-19 risk (86, 87).…”

Replication of LZTFL1 gene region as a susceptibility locus for COVID-19 in Latvian population

“…All of these variants are believed to represent the region to be a remnant of Neanderthal gene pool introgression into the modern human population (Zeberg and Pääbo, 2020). LZFTL1 gene has been implicated in ciliogenesis and intracellular trafficking of ciliary proteins, probably impacting airway epithelial cell function (Promchan et al, 2020;Shelton et al, 2021). Even though the primary analysis was performed on the case group that included all patients regardless of severity, there is an obvious bias toward the inclusion of symptomatic patients as they are more likely to be tested for the SARS-CoV-2 presence than asymptomatic cases.…”