La-related protein 1 (LARP1) is a 150 kDa protein that in humans is encoded by the LARP1 gene. LARP1 is a novel target of the mammalian target of rapamycin complex 1 (mTORC1) signaling pathway, a circuitry often hyperactivated in cancer which regulates cell growth and proliferation primarily through the regulation of protein synthesis. LARP1 is the largest of a 7-member family of LARP proteins (others are: LARP1B, LARP3 (aka genuine La or SSB), LARP4A, LARP4B, LARP6 and LARP7). All LARP proteins, including human LARPs, contain 2 conserved regions. The first conserved region shares homology with La proteins (called the La motif, see SSB) whereas the second conserved region (called the LA- motif) is restricted to LARP proteins. LARP1 and 1B also contain a conserved "DM15 region" within their C-terminus. This region is unique and has been shown to be required for RNA-binding. Mouse Larp1 is expressed in dorsal root ganglia and spinal cord, as well as in developing organs characterized by epithelial-mesenchymal interactions. Human LARP1 is present at low levels in normal, non-embryonic cells but is highly expressed in epithelial cancers (such as ovarian, colorectal, prostate, non-small cell lung, hepatocellular and cervical cancers). Some studies have shown that high levels of LARP1 protein correlate with worse prognosis in cancer patients.
Background References
1. Berman AJ et al. Controversies around the function of LARP1. RNA Biol. 2021 Feb
2. Mattijssen S et al. LARP1 and LARP4: up close with PABP for mRNA 3\' poly(A) protection and stabilization. RNA Biol. 2021 Feb
Western blot analysis of LARP1 on different lysates with Rabbit anti-LARP1 antibody (HA723425) at 1/5,000 dilution.
Lane 1: HeLa cell lysate Lane 2: HEK-293 cell lysate Lane 3: Jurkat cell lysate Lane 4: 786-0 cell lysate Lane 5: COS-1 cell lysate
Lysates/proteins at 15 µg/Lane.
Predicted band size: 124 kDa Observed band size: 150 kDa
Exposure time: 30 seconds; ECL: K1801;
4-20% SDS-PAGE gel.
Proteins were transferred to a PVDF membrane and blocked with 5% NFDM/TBST for 1 hour at room temperature. The primary antibody (HA723425) at 1/5,000 dilution was used in 5% NFDM/TBST at 4℃ overnight. Goat Anti-Rabbit IgG - HRP Secondary Antibody (HA1001) at 1/50,000 dilution was used for 1 hour at room temperature.
Immunocytochemistry analysis of HeLa cells labeling LARP1 with Rabbit anti-LARP1 antibody (HA723425) at 1/100 dilution.
Cells were fixed in 4% paraformaldehyde for 15 minutes at room temperature, permeabilized with 0.1% Triton X-100 in PBS for 15 minutes at room temperature, then blocked with 1% BSA in 10% negative goat serum for 1 hour at room temperature. Cells were then incubated with Rabbit anti-LARP1 antibody (HA723425) at 1/100 dilution in 1% BSA in PBST overnight at 4 ℃. Goat Anti-Rabbit IgG H&L (iFluor™ 488, HA1121) was used as the secondary antibody at 1/1,000 dilution. PBS instead of the primary antibody was used as the secondary antibody only control. Nuclear DNA was labelled in blue with DAPI.
Beta tubulin (HA601187, red) was stained at 1/100 dilution overnight at +4℃. Goat Anti-Mouse IgG H&L (iFluor™ 594, HA1126) was used as the secondary antibody at 1/1,000 dilution.
Immunocytochemistry analysis of COS-1 cells labeling LARP1 with Rabbit anti-LARP1 antibody (HA723425) at 1/50 dilution.
Cells were fixed in 4% paraformaldehyde for 15 minutes at room temperature, permeabilized with 0.1% Triton X-100 in PBS for 15 minutes at room temperature, then blocked with 1% BSA in 10% negative goat serum for 1 hour at room temperature. Cells were then incubated with Rabbit anti-LARP1 antibody (HA723425) at 1/50 dilution in 1% BSA in PBST overnight at 4 ℃. Goat Anti-Rabbit IgG H&L (iFluor™ 488, HA1121) was used as the secondary antibody at 1/1,000 dilution. PBS instead of the primary antibody was used as the secondary antibody only control. Nuclear DNA was labelled in blue with DAPI.
Beta tubulin (HA601187, red) was stained at 1/100 dilution overnight at +4℃. Goat Anti-Mouse IgG H&L (iFluor™ 594, HA1126) was used as the secondary antibody at 1/1,000 dilution.
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